1.What is CSS?
1. CSS stands for Cascading Style Sheets and is a simple styling language which allows attaching style to HTML elements. Every element type as well as every occurrence of a specific element within that type can be declared an unique style, e.g. margins, positioning, color or size.
2. CSS is a web standard that describes style for XML/HTML documents.
3. CSS is a language that adds style (colors, images, borders, margins…) to your site. It’s really that simple. CSS is not used to put any content on your site, it’s just there to take the content you have and make it pretty. First thing you do is link a CSS-file to your HTML document. Do this by adding this line:
<link rel="stylesheet" href="style.css"
type="text/css">
The line should be placed in between your <head> and </head> tags. If you have several pages you could add the exact same line to all of them and they will all use the same stylesheet, but more about that later. Let’s look inside the file “style.css” we just linked to.
h1 {
font-size: 40px;
height: 200px;
}
.warning {
color: Red;
font-weight: bold;
}
#footer {
background-color: Gray;
}
4. Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g. fonts, colors, spacing) to Web documents. This is also where information meets the artistic abilities of a web-designer. CSS helps you spice up your web-page and make it look neat in wide variety of aspects.
2.What are Cascading Style Sheets?
A Cascading Style Sheet (CSS) is a list of statements (also known as rules) that can assign various rendering properties to HTML elements. Style rules can be specified for a single element occurrence, multiple elements, an entire document, or even multiple documents at once. It is possible to specify many different rules for an element in different locations using different methods. All these rules are collected and merged (known as a "cascading" of styles) when the document is rendered to form a single style rule for each element.
3.How do I center block-elements with CSS1?
There are two ways of centering block level elements:
1. By setting the properties margin-left and margin-right to auto and width to some explicit value:
BODY {width: 30em; background: cyan;}
P {width: 22em; margin-left: auto; margin-right: auto}
In this case, the left and right margins will each be four ems wide, since they equally split up the eight ems left over from (30em - 22em). Note that it was not necessary to set an explicit width for the BODY element; it was done here to keep the math clean.
Another example:
TABLE {margin-left: auto; margin-right: auto; width: 400px;}
In most legacy browsers, a table's width is by default determined by its content. In CSS-conformant browsers, the complete width of any element (including tables) defaults to the full width of its parent element's content area. As browser become more conformant, authors will need to be aware of the potential impact on their designs.
4.If background and color should always be set together, why do they exist as separate properties?
There are several reasons for this. First, style sheets become more legible -- both for humans and machines. The background property is already the most complex property in CSS1 and combining it with color would make it even more complex. Second, color inherits, but background doesn't and this would be a source of confusion.
5.What is class?
Class is a group of 1) instances of the same element to which an unique style can be attached or 2) instances of different elements to which the same style can be attached.
1) The rule P {color: red} will display red text in all paragraphs. By classifying the selector P different style can be attached to each class allowing the display of some paragraphs in one style and some other paragraphs in another style.
2) A class can also be specified without associating a specific element to it and then attached to any element which is to be styled in accordance with it's declaration. All elements to which a specific class is attached will have the same style.
To classify an element add a period to the selector followed by an unique name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters). (Note: text between /* and */ are my comments).
CSS
P.name1 {color: red} /* one class of P selector */
P.name2 {color: blue} /* another class of P selector */
.name3 {color: green} /* can be attached to any element */
HTML
<P class=name1>This paragraph will be red</P>
<P class=name2>This paragraph will be blue</P>
<P class=name3>This paragraph will be green</P>
<LI class=name3>This list item will be green</LI>
It is a good practice to name classes according to their function than their appearance; e.g. P.fotnote and not P.green. In CSS1 only one class can be attached to a selector. CSS2 allows attaching more classes, e.g.:
P.name1.name2.name3 {declaration} <P class="name1 name2 name2">This paragraph has three classes attached</P>
6.What is grouping ?
Grouping is gathering (1) into a comma separated list two or more selectors that share the same style or (2) into a semicolon separated list two or more declarations that are attached to the same selector (2).
1. The selectors LI, P with class name .first and class .footnote share the same style, e.g.:
LI {font-style: italic}
P.first {font-style: italic}
.footnote {font-style: italic}
To reduce the size of style sheets and also save some typing time they can all be grouped in one list.
LI, P.first, .footnote {font-style: italic}
2. The declarations {font-style: italic} and {color: red} can be attached to one selector, e.g.:
H2 {font-style: italic}
H2 {color: red}
and can also be grouped into one list:
H2 {font-style: italic; color: red}
7.What is external Style Sheet? How to link?
External Style Sheet is a template/document/file containing style information which can be linked with any number of HTML documents. This is a very convenient way of formatting the entire site as well as restyling it by editing just one file. The file is linked with HTML documents via the LINK element inside the HEAD element. Files containing style information must have extension .css, e.g. style.css. <HEAD> <LINK REL=STYLESHEET HREF="style.css" TYPE="text/css"> </HEAD>
8.Is CSS case sensitive?
Cascading Style Sheets (CSS) is not case sensitive. However, font families, URLs to images, and other direct references with the style sheet may be.
The trick is that if you write a document using an XML declaration and an XHTML doctype, then the CSS class names will be case sensitive for some browsers.
It is a good idea to avoid naming classes where the only difference is the case, for example:
div.myclass { ...}
div.myClass { ... }
If the DOCTYPE or XML declaration is ever removed from your pages, even by mistake, the last instance of the style will be used, regardless of case.
9.What are Style Sheets?
Style Sheets are templates, very similar to templates in desktop publishing applications, containing a collection of rules declared to various selectors (elements).
10.What is embedded style? How to link?
Embedded style is the style attached to one specific document. The style information is specified as a content of the STYLE element inside the HEAD element and will apply to the entire document.
<HEAD>
<STYLE TYPE="text/css">
<!--
P {text-indent: 10pt}
-->
</STYLE>
</HEAD>
Note: The styling rules are written as a HTML comment, that is, between <!-- and --> to hide the content in browsers without CSS support which would otherwise be displayed.
11.What is ID selector?
ID selector is an individually identified (named) selector to which a specific style is declared. Using the ID attribute the declared style can then be associated with one and only one HTML element per document as to differentiate it from all other elements. ID selectors are created by a character # followed by the selector's name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit.
#abc123 {color: red; background: black}
<P ID=abc123>This and only this element can be identified as abc123 </P>
12.What is contextual selector?
Contextual selector is a selector that addresses specific occurrence of an element. It is a string of individual selectors separated by white space, a search pattern, where only the last element in the pattern is addressed providing it matches the specified context.
TD P CODE {color: red}
The element CODE will be displayed in red but only if it occurs in the context of the element P which must occur in the context of the element TD.
TD P CODE, H1 EM {color: red}
The element CODE will be displayed in red as described above AND the element EM will also be red but only if it occurs in the context of H1
P .footnote {color: red}
Any element with CLASS footnote will be red but only if it occurs in the context of P
P .footnote [lang]{color: red}
Any element with attribute LANG will be red but only if it is classed as "footnote" and occurs in the context of P
13.How do I have a background image that isn't tiled?
Specify the background-repeat property as no-repeat. You can also use the background property as a shortcut for specifying multiple background-* properties at once. Here's an example:
BODY {background: #FFF url(watermark.jpg) no-repeat;}
14.Why do style sheets exist?
SGML (of which HTML is a derivative) was meant to be a device-independent method for conveying a document's structural and semantic content (its meaning.) It was never meant to convey physical formatting information. HTML has crossed this line and now contains many elements and attributes which specify visual style and formatting information. One of the main reasons for style sheets is to stop the creation of new HTML physical formatting constructs and once again separate style information from document content.
15.What is inline style? How to link?
Inline style is the style attached to one specific element. The style is specified directly in the start tag as a value of the STYLE attribute and will apply exclusively to this specific element occurrence.
<P STYLE="text-indent: 10pt">Indented paragraph</P>
16.How do I combine multiple sheets into one?
To combine multiple/partial style sheets into one set the TITLE attribute taking one and the same value to the LINK element. The combined style will apply as a preferred style, e.g.:
<LINK REL=Stylesheet HREF="default.css" TITLE="combined">
<LINK REL=Stylesheet HREF="fonts.css" TITLE="combined">
<LINK REL=Stylesheet HREF="tables.css" TITLE="combined">
17.What is parent-child selector?
Parent-child selector is a selector representing the direct descendent of a parent element. Parent-child selectors are created by listing two or more tilde (~) separated selectors.
BODY ~ P {background: red; color: white}
The P element will be declared the specified style only if it directly descends from the BODY element:
<BODY> <P>Red and white paragraph </P> </BODY>
BODY ~ P ~ EM {background: red; color: white}
The EM element will be declared the specified style only if it directly descends from the P element which in its turn directly descends from the BODY element:
< <P> <EM>Red and white EM </EM> </P> </BODY>
18.How do I have a fixed (non-scrolling) background image?
With CSS, you can use the background-attachment property. The background attachment can be included in the shorthand background property, as in this example:
body {
background: white url(example.gif) fixed ;
color: black ;
}
Note that this CSS is supported by Internet Explorer, Mozilla, Firefox Opera, Safari, and other browsers. In contrast, Microsoft's proprietary BGPROPERTIES attribute is supported only by Internet Explorer.
19.Why use Style Sheets?
Style sheets allow a much greater degree of layout and display control than has ever been possible thus far in HTML. The amount of format coding necessary to control display characteristics can be greatly reduced through the use of external style sheets which can be used by a group of documents. Also, multiple style sheets can be integrated from different sources to form a cohesive tapestry of styles for a document. Style sheets are also backward compatible - They can be mixed with HTML styling elements and attributes so that older browsers can view content as intended.
20.What does the "Cascading" in "Cascading Style Sheets" mean?
Style Sheets allow style information to be specified from many locations. Multiple (partial) external style sheets can be referenced to reduce redundancy, and both authors as well as readers can specify style preferences. In addition, three main methods can be employed by an author to add style information to HTML documents, and multiple approaches for style control are available in each of these methods. In the end, style can be specified for a single element using any, or all, of these methods. What style is to be used when there is a direct conflict between style specifications for an element?
Cascading comes to the rescue. A document can have styles specified using all of these methods, but all the information will be reduced to a single, cohesive "virtual" Style Sheet. Conflict resolution is based on each style rule having an assigned weight according to its importance in the scheme of things. A rule with a higher overall importance will carry a higher weight. This will be used in place of a competing style rule with a lower weight/importance. A hierarchy of competing styles is thus formed creating a "cascade" of styles according to their assigned weights. The algorithm used to determine this cascading weight scale is fairly complex.
21.What is CSS rule 'at-rule'?
There are two types of CSS rules: ruleset and at-rule. At-rule is a rule that applies to the whole style sheet and not to a specific selector only (like in ruleset). They all begin with the @ symbol followed by a keyword made up of letters a-z, A-Z, digits 0-9, dashes and escaped characters, e.g. @import or @font-face.
22.What is selector?
CSS selector is equivalent of HTML element(s). It is a string identifying to which element(s) the corresponding declaration(s) will apply and as such the link between the HTML document and the style sheet.
For example in P {text-indent: 10pt} the selector is P and is called type selector as it matches all instances of this element type in the document.
in P, UL {text-indent: 10pt} the selector is P and UL (see grouping); in .class {text-indent: 10pt} the selector is .class (see class selector).
23.What is CLASS selector?
Class selector is a "stand alone" class to which a specific style is declared. Using the CLASS attribute the declared style can then be associated with any HTML element. The class selectors are created by a period followed by the class's name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).It is a good practice to name classes according to their function than their appearance.
.footnote {font: 70%} /* class as selector */
<ADDRESS CLASS=footnote/>This element is associated with the CLASS footnote</ADDRESS>
<P CLASS=footnote>And so is this</P>
24.What is CSS declaration?
CSS declaration is style attached to a specific selector. It consists of two parts; property which is equivalent of HTML attribute, e.g. text-indent: and value which is equivalent of HTML value, e.g. 10pt. NOTE: properties are always ended with a colon.
25.What is 'important' declaration?
Important declaration is a declaration with increased weight. Declaration with increased weight will override declarations with normal weight. If both reader's and author's style sheet contain statements with important declarations the author's declaration will override the reader's.
BODY {background: white ! important; color: black}
In the example above the background property has increased weight while the color property has normal.
26.What is cascade?
Cascade is a method of defining the weight (importance) of individual styling rules thus allowing conflicting rules to be sorted out should such rules apply to the same selector.
Declarations with increased weight take precedence over declaration with normal weight:
P {color: white ! important} /* increased weight */
P (color: black} /* normal weight */
27.Are Style Sheets case sensitive?
No. Style sheets are case insensitive. Whatever is case insensitive in HTML is also case insensitive in CSS. However, parts that are not under control of CSS like font family names and URLs can be case sensitive - IMAGE.gif and image.gif is not the same file.
28.Can I include comments in my Style Sheet?
Yes. Comments can be written anywhere where whitespace is allowed and are treated as white space themselves. Anything written between /* and */ is treated as a comment (white space). NOTE: Comments cannot be nested.
29.Which characters can CSS-names contain?
The CSS-names; names of selectors, classes and IDs can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code. The names cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).
30.What browsers support style sheets? To what extent?
Microsoft's Internet Explorer version 3.0 Beta 2 and above supports CSS, as does Netscape Communicator 4.0 Beta 2 and above and Opera 3.5 and above. Take note that the early implementations in these browsers did not support ALL of the properties and syntax described in the full CSS1 specification and beyond. Later versions have been getting much closer to full CSS1 compliance, but then comes the next hurdle - CSS2...it was such a big leap over CSS1 that it has taken the browsers years to come close to supporting a majority of CSS2's features. Mozilla and Opera's current versions both offer excellent CSS standards compliance. The Macintosh version of Internet Explorer is said to be very impressive in its CSS capabilities as well, but PC IE lags behind these implementations. Quite a few other implementations of CSS now exist in browsers that are not as widely-used (such as Amaya, Arena and Emacs-W3), but coverage of features in these documents currently only covers Internet Explorer, NCSA Mosaic, Netscape and Opera browsers.
31.What is shorthand property?
Shorthand property is a property made up of individual properties that have a common "addressee". For example properties: font-weight, font-style, font-variant, font-size, font-family, refer to the font. To reduce the size of style sheets and also save some keystrokes as well as bandwidth they can all be specified as one shorthand property font, e.g.:
H1 {font-weight: bold;
font-style: italic;
font-variant: small-caps;
font-size: 160%;
font-family: serif}
can be all shorthanded to a space separated list:
H1 {font: bold italic small-caps 160% serif}
Note: To make things even simpler the line-height property can be specified together with the font-size property:
H1 {font: bold italic small-caps 160%/170% serif}
32.What is value?
Value is a 'physical' characteristic of the property. Property declares what should be formatted, e.g. FONT while value suggests how the property should be formatted, e.g. 12pt. By setting the value 12pt to the property FONT it is suggested that the formatted text be displayed in a 12 point font. There must always be a corresponding property to each value or set of values.
H1 {font: bold 180%}
In the example above the H1 selector is declared the FONT property which in its turn is declared the values BOLD and 180%.
The values suggesting alternatives are specified in a comma separated list, e.g.
H1 {font-family: font1, font2}
33.What is initial value?
Initial value is a default value of the property, that is the value given to the root element of the document tree. All properties have an initial value. If no specific value is set and/or if a property is not inherited the initial value is used. For example the background property is not inherited, however, the background of the parent element shines through because the initial value of background property is transparent.
<P style="background: red">Hello <strong>World </strong> </P>
Content of the element P will also have red background
34.How frustrating is it to write a specification knowing that you're at the browser vendors' mercy?
That's part of the game. I don't think any specification has a birthright to be fully supported by all browsers. There should be healthy competition between different specifications. I believe simple, author-friendly specifications will prevail in this environment.
Microformats are another way of developing new formats. Instead of having to convince browser vendors to support your favorite specification, microformats add semantics to HTML through the CLASS attribute. And style it with CSS.
35.How far can CSS be taken beyond the web page--that is, have generalized or non-web specific features for such things as page formatting or type setting?
Yes, it's possible to take CSS further in several directions. W3C just published a new Working Draft which describes features for printing, e.g., footnotes, cross-references, and even generated indexes.
Another great opportunity for CSS is Web Applications. Just like documents, applications need to be styled and CSS is an intrinsic component of AJAX. The "AJAX" name sounds great.
36.How To Style Table Cells?
Margin, Border and Padding are difficult to apply to inline elements. Officially, the <TD> tag is a block level element because it can contain other block level elements (see Basics - Elements).
If you need to set special margins, borders, or padding inside a table cell, then use this markup:
<td>
yourtext </div></td>
to apply the CSS rules to the div inside the cell. </p>
37.How To Style Forms?
Forms and form elements like SELECT, INPUT etc. can be styled with CSS - partially.
Checkboxes and Radiobuttons do not yet accept styles, and Netscape 4.xx has certain issues, but here is a tutorial that explains the application of CSS Styles on Form Elements.
38.Must I quote property values?
Generally no. However, values containing white spaces, e.g. font-family names should be quoted as whitespaces surrounding the font name are ignored and whitespaces inside the font name are converted to a single space, thus font names made up of more than one word (e.g.) 'Times New Roman' are interpreted as three different names: Times, New and Roman.
39.Do any WYSIWYG editors support the creation of Style Sheets? Any text-based HTML editors?
As support for CSS in browsers has matured in the last year, both WYSIWYG and Text-based HTML editors have appeared that allow the creation or the assistance of creating Cascading Style Sheet syntax. There are now at least two dozen editors supporting CSS syntax in some form. The W3C maintains an up-to-date list of these WYSIWYG and text-based editors.
40.To what are partial URLs relative?
Partial URLs are relative to the source of the style sheet. The style sheet source can either be linked or embedded. To which source partial URLs are relative to depends on their occurrence.
If a partial URL occurs in a linked style sheet then it is relative to the linked style sheet. The URL of the linked style sheet is the URL of the directory where the sheet is kept.
If a partial URL occurs in an embedded style sheet then it is relative to the embedded style sheet. The URL of the embedded style sheet is the URL of the HTML document in which the sheet is embedded.
Note that Navigator 4.x treats partial URLs as being relative to the HTML document, regardless of the place where the partial URL occurs. This is a serious bug which forces most authors to use absolute URLs in their CSS.
1. CSS stands for Cascading Style Sheets and is a simple styling language which allows attaching style to HTML elements. Every element type as well as every occurrence of a specific element within that type can be declared an unique style, e.g. margins, positioning, color or size.
2. CSS is a web standard that describes style for XML/HTML documents.
3. CSS is a language that adds style (colors, images, borders, margins…) to your site. It’s really that simple. CSS is not used to put any content on your site, it’s just there to take the content you have and make it pretty. First thing you do is link a CSS-file to your HTML document. Do this by adding this line:
<link rel="stylesheet" href="style.css"
type="text/css">
The line should be placed in between your <head> and </head> tags. If you have several pages you could add the exact same line to all of them and they will all use the same stylesheet, but more about that later. Let’s look inside the file “style.css” we just linked to.
h1 {
font-size: 40px;
height: 200px;
}
.warning {
color: Red;
font-weight: bold;
}
#footer {
background-color: Gray;
}
4. Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g. fonts, colors, spacing) to Web documents. This is also where information meets the artistic abilities of a web-designer. CSS helps you spice up your web-page and make it look neat in wide variety of aspects.
2.What are Cascading Style Sheets?
A Cascading Style Sheet (CSS) is a list of statements (also known as rules) that can assign various rendering properties to HTML elements. Style rules can be specified for a single element occurrence, multiple elements, an entire document, or even multiple documents at once. It is possible to specify many different rules for an element in different locations using different methods. All these rules are collected and merged (known as a "cascading" of styles) when the document is rendered to form a single style rule for each element.
3.How do I center block-elements with CSS1?
There are two ways of centering block level elements:
1. By setting the properties margin-left and margin-right to auto and width to some explicit value:
BODY {width: 30em; background: cyan;}
P {width: 22em; margin-left: auto; margin-right: auto}
In this case, the left and right margins will each be four ems wide, since they equally split up the eight ems left over from (30em - 22em). Note that it was not necessary to set an explicit width for the BODY element; it was done here to keep the math clean.
Another example:
TABLE {margin-left: auto; margin-right: auto; width: 400px;}
In most legacy browsers, a table's width is by default determined by its content. In CSS-conformant browsers, the complete width of any element (including tables) defaults to the full width of its parent element's content area. As browser become more conformant, authors will need to be aware of the potential impact on their designs.
4.If background and color should always be set together, why do they exist as separate properties?
There are several reasons for this. First, style sheets become more legible -- both for humans and machines. The background property is already the most complex property in CSS1 and combining it with color would make it even more complex. Second, color inherits, but background doesn't and this would be a source of confusion.
5.What is class?
Class is a group of 1) instances of the same element to which an unique style can be attached or 2) instances of different elements to which the same style can be attached.
1) The rule P {color: red} will display red text in all paragraphs. By classifying the selector P different style can be attached to each class allowing the display of some paragraphs in one style and some other paragraphs in another style.
2) A class can also be specified without associating a specific element to it and then attached to any element which is to be styled in accordance with it's declaration. All elements to which a specific class is attached will have the same style.
To classify an element add a period to the selector followed by an unique name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters). (Note: text between /* and */ are my comments).
CSS
P.name1 {color: red} /* one class of P selector */
P.name2 {color: blue} /* another class of P selector */
.name3 {color: green} /* can be attached to any element */
HTML
<P class=name1>This paragraph will be red</P>
<P class=name2>This paragraph will be blue</P>
<P class=name3>This paragraph will be green</P>
<LI class=name3>This list item will be green</LI>
It is a good practice to name classes according to their function than their appearance; e.g. P.fotnote and not P.green. In CSS1 only one class can be attached to a selector. CSS2 allows attaching more classes, e.g.:
P.name1.name2.name3 {declaration} <P class="name1 name2 name2">This paragraph has three classes attached</P>
6.What is grouping ?
Grouping is gathering (1) into a comma separated list two or more selectors that share the same style or (2) into a semicolon separated list two or more declarations that are attached to the same selector (2).
1. The selectors LI, P with class name .first and class .footnote share the same style, e.g.:
LI {font-style: italic}
P.first {font-style: italic}
.footnote {font-style: italic}
To reduce the size of style sheets and also save some typing time they can all be grouped in one list.
LI, P.first, .footnote {font-style: italic}
2. The declarations {font-style: italic} and {color: red} can be attached to one selector, e.g.:
H2 {font-style: italic}
H2 {color: red}
and can also be grouped into one list:
H2 {font-style: italic; color: red}
7.What is external Style Sheet? How to link?
External Style Sheet is a template/document/file containing style information which can be linked with any number of HTML documents. This is a very convenient way of formatting the entire site as well as restyling it by editing just one file. The file is linked with HTML documents via the LINK element inside the HEAD element. Files containing style information must have extension .css, e.g. style.css. <HEAD> <LINK REL=STYLESHEET HREF="style.css" TYPE="text/css"> </HEAD>
8.Is CSS case sensitive?
Cascading Style Sheets (CSS) is not case sensitive. However, font families, URLs to images, and other direct references with the style sheet may be.
The trick is that if you write a document using an XML declaration and an XHTML doctype, then the CSS class names will be case sensitive for some browsers.
It is a good idea to avoid naming classes where the only difference is the case, for example:
div.myclass { ...}
div.myClass { ... }
If the DOCTYPE or XML declaration is ever removed from your pages, even by mistake, the last instance of the style will be used, regardless of case.
9.What are Style Sheets?
Style Sheets are templates, very similar to templates in desktop publishing applications, containing a collection of rules declared to various selectors (elements).
10.What is embedded style? How to link?
Embedded style is the style attached to one specific document. The style information is specified as a content of the STYLE element inside the HEAD element and will apply to the entire document.
<HEAD>
<STYLE TYPE="text/css">
<!--
P {text-indent: 10pt}
-->
</STYLE>
</HEAD>
Note: The styling rules are written as a HTML comment, that is, between <!-- and --> to hide the content in browsers without CSS support which would otherwise be displayed.
11.What is ID selector?
ID selector is an individually identified (named) selector to which a specific style is declared. Using the ID attribute the declared style can then be associated with one and only one HTML element per document as to differentiate it from all other elements. ID selectors are created by a character # followed by the selector's name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit.
#abc123 {color: red; background: black}
<P ID=abc123>This and only this element can be identified as abc123 </P>
12.What is contextual selector?
Contextual selector is a selector that addresses specific occurrence of an element. It is a string of individual selectors separated by white space, a search pattern, where only the last element in the pattern is addressed providing it matches the specified context.
TD P CODE {color: red}
The element CODE will be displayed in red but only if it occurs in the context of the element P which must occur in the context of the element TD.
TD P CODE, H1 EM {color: red}
The element CODE will be displayed in red as described above AND the element EM will also be red but only if it occurs in the context of H1
P .footnote {color: red}
Any element with CLASS footnote will be red but only if it occurs in the context of P
P .footnote [lang]{color: red}
Any element with attribute LANG will be red but only if it is classed as "footnote" and occurs in the context of P
13.How do I have a background image that isn't tiled?
Specify the background-repeat property as no-repeat. You can also use the background property as a shortcut for specifying multiple background-* properties at once. Here's an example:
BODY {background: #FFF url(watermark.jpg) no-repeat;}
14.Why do style sheets exist?
SGML (of which HTML is a derivative) was meant to be a device-independent method for conveying a document's structural and semantic content (its meaning.) It was never meant to convey physical formatting information. HTML has crossed this line and now contains many elements and attributes which specify visual style and formatting information. One of the main reasons for style sheets is to stop the creation of new HTML physical formatting constructs and once again separate style information from document content.
15.What is inline style? How to link?
Inline style is the style attached to one specific element. The style is specified directly in the start tag as a value of the STYLE attribute and will apply exclusively to this specific element occurrence.
<P STYLE="text-indent: 10pt">Indented paragraph</P>
16.How do I combine multiple sheets into one?
To combine multiple/partial style sheets into one set the TITLE attribute taking one and the same value to the LINK element. The combined style will apply as a preferred style, e.g.:
<LINK REL=Stylesheet HREF="default.css" TITLE="combined">
<LINK REL=Stylesheet HREF="fonts.css" TITLE="combined">
<LINK REL=Stylesheet HREF="tables.css" TITLE="combined">
17.What is parent-child selector?
Parent-child selector is a selector representing the direct descendent of a parent element. Parent-child selectors are created by listing two or more tilde (~) separated selectors.
BODY ~ P {background: red; color: white}
The P element will be declared the specified style only if it directly descends from the BODY element:
<BODY> <P>Red and white paragraph </P> </BODY>
BODY ~ P ~ EM {background: red; color: white}
The EM element will be declared the specified style only if it directly descends from the P element which in its turn directly descends from the BODY element:
< <P> <EM>Red and white EM </EM> </P> </BODY>
18.How do I have a fixed (non-scrolling) background image?
With CSS, you can use the background-attachment property. The background attachment can be included in the shorthand background property, as in this example:
body {
background: white url(example.gif) fixed ;
color: black ;
}
Note that this CSS is supported by Internet Explorer, Mozilla, Firefox Opera, Safari, and other browsers. In contrast, Microsoft's proprietary BGPROPERTIES attribute is supported only by Internet Explorer.
19.Why use Style Sheets?
Style sheets allow a much greater degree of layout and display control than has ever been possible thus far in HTML. The amount of format coding necessary to control display characteristics can be greatly reduced through the use of external style sheets which can be used by a group of documents. Also, multiple style sheets can be integrated from different sources to form a cohesive tapestry of styles for a document. Style sheets are also backward compatible - They can be mixed with HTML styling elements and attributes so that older browsers can view content as intended.
20.What does the "Cascading" in "Cascading Style Sheets" mean?
Style Sheets allow style information to be specified from many locations. Multiple (partial) external style sheets can be referenced to reduce redundancy, and both authors as well as readers can specify style preferences. In addition, three main methods can be employed by an author to add style information to HTML documents, and multiple approaches for style control are available in each of these methods. In the end, style can be specified for a single element using any, or all, of these methods. What style is to be used when there is a direct conflict between style specifications for an element?
Cascading comes to the rescue. A document can have styles specified using all of these methods, but all the information will be reduced to a single, cohesive "virtual" Style Sheet. Conflict resolution is based on each style rule having an assigned weight according to its importance in the scheme of things. A rule with a higher overall importance will carry a higher weight. This will be used in place of a competing style rule with a lower weight/importance. A hierarchy of competing styles is thus formed creating a "cascade" of styles according to their assigned weights. The algorithm used to determine this cascading weight scale is fairly complex.
21.What is CSS rule 'at-rule'?
There are two types of CSS rules: ruleset and at-rule. At-rule is a rule that applies to the whole style sheet and not to a specific selector only (like in ruleset). They all begin with the @ symbol followed by a keyword made up of letters a-z, A-Z, digits 0-9, dashes and escaped characters, e.g. @import or @font-face.
22.What is selector?
CSS selector is equivalent of HTML element(s). It is a string identifying to which element(s) the corresponding declaration(s) will apply and as such the link between the HTML document and the style sheet.
For example in P {text-indent: 10pt} the selector is P and is called type selector as it matches all instances of this element type in the document.
in P, UL {text-indent: 10pt} the selector is P and UL (see grouping); in .class {text-indent: 10pt} the selector is .class (see class selector).
23.What is CLASS selector?
Class selector is a "stand alone" class to which a specific style is declared. Using the CLASS attribute the declared style can then be associated with any HTML element. The class selectors are created by a period followed by the class's name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).It is a good practice to name classes according to their function than their appearance.
.footnote {font: 70%} /* class as selector */
<ADDRESS CLASS=footnote/>This element is associated with the CLASS footnote</ADDRESS>
<P CLASS=footnote>And so is this</P>
24.What is CSS declaration?
CSS declaration is style attached to a specific selector. It consists of two parts; property which is equivalent of HTML attribute, e.g. text-indent: and value which is equivalent of HTML value, e.g. 10pt. NOTE: properties are always ended with a colon.
25.What is 'important' declaration?
Important declaration is a declaration with increased weight. Declaration with increased weight will override declarations with normal weight. If both reader's and author's style sheet contain statements with important declarations the author's declaration will override the reader's.
BODY {background: white ! important; color: black}
In the example above the background property has increased weight while the color property has normal.
26.What is cascade?
Cascade is a method of defining the weight (importance) of individual styling rules thus allowing conflicting rules to be sorted out should such rules apply to the same selector.
Declarations with increased weight take precedence over declaration with normal weight:
P {color: white ! important} /* increased weight */
P (color: black} /* normal weight */
27.Are Style Sheets case sensitive?
No. Style sheets are case insensitive. Whatever is case insensitive in HTML is also case insensitive in CSS. However, parts that are not under control of CSS like font family names and URLs can be case sensitive - IMAGE.gif and image.gif is not the same file.
28.Can I include comments in my Style Sheet?
Yes. Comments can be written anywhere where whitespace is allowed and are treated as white space themselves. Anything written between /* and */ is treated as a comment (white space). NOTE: Comments cannot be nested.
29.Which characters can CSS-names contain?
The CSS-names; names of selectors, classes and IDs can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code. The names cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).
30.What browsers support style sheets? To what extent?
Microsoft's Internet Explorer version 3.0 Beta 2 and above supports CSS, as does Netscape Communicator 4.0 Beta 2 and above and Opera 3.5 and above. Take note that the early implementations in these browsers did not support ALL of the properties and syntax described in the full CSS1 specification and beyond. Later versions have been getting much closer to full CSS1 compliance, but then comes the next hurdle - CSS2...it was such a big leap over CSS1 that it has taken the browsers years to come close to supporting a majority of CSS2's features. Mozilla and Opera's current versions both offer excellent CSS standards compliance. The Macintosh version of Internet Explorer is said to be very impressive in its CSS capabilities as well, but PC IE lags behind these implementations. Quite a few other implementations of CSS now exist in browsers that are not as widely-used (such as Amaya, Arena and Emacs-W3), but coverage of features in these documents currently only covers Internet Explorer, NCSA Mosaic, Netscape and Opera browsers.
31.What is shorthand property?
Shorthand property is a property made up of individual properties that have a common "addressee". For example properties: font-weight, font-style, font-variant, font-size, font-family, refer to the font. To reduce the size of style sheets and also save some keystrokes as well as bandwidth they can all be specified as one shorthand property font, e.g.:
H1 {font-weight: bold;
font-style: italic;
font-variant: small-caps;
font-size: 160%;
font-family: serif}
can be all shorthanded to a space separated list:
H1 {font: bold italic small-caps 160% serif}
Note: To make things even simpler the line-height property can be specified together with the font-size property:
H1 {font: bold italic small-caps 160%/170% serif}
32.What is value?
Value is a 'physical' characteristic of the property. Property declares what should be formatted, e.g. FONT while value suggests how the property should be formatted, e.g. 12pt. By setting the value 12pt to the property FONT it is suggested that the formatted text be displayed in a 12 point font. There must always be a corresponding property to each value or set of values.
H1 {font: bold 180%}
In the example above the H1 selector is declared the FONT property which in its turn is declared the values BOLD and 180%.
The values suggesting alternatives are specified in a comma separated list, e.g.
H1 {font-family: font1, font2}
33.What is initial value?
Initial value is a default value of the property, that is the value given to the root element of the document tree. All properties have an initial value. If no specific value is set and/or if a property is not inherited the initial value is used. For example the background property is not inherited, however, the background of the parent element shines through because the initial value of background property is transparent.
<P style="background: red">Hello <strong>World </strong> </P>
Content of the element P will also have red background
34.How frustrating is it to write a specification knowing that you're at the browser vendors' mercy?
That's part of the game. I don't think any specification has a birthright to be fully supported by all browsers. There should be healthy competition between different specifications. I believe simple, author-friendly specifications will prevail in this environment.
Microformats are another way of developing new formats. Instead of having to convince browser vendors to support your favorite specification, microformats add semantics to HTML through the CLASS attribute. And style it with CSS.
35.How far can CSS be taken beyond the web page--that is, have generalized or non-web specific features for such things as page formatting or type setting?
Yes, it's possible to take CSS further in several directions. W3C just published a new Working Draft which describes features for printing, e.g., footnotes, cross-references, and even generated indexes.
Another great opportunity for CSS is Web Applications. Just like documents, applications need to be styled and CSS is an intrinsic component of AJAX. The "AJAX" name sounds great.
36.How To Style Table Cells?
Margin, Border and Padding are difficult to apply to inline elements. Officially, the <TD> tag is a block level element because it can contain other block level elements (see Basics - Elements).
If you need to set special margins, borders, or padding inside a table cell, then use this markup:
<td>
yourtext </div></td>
to apply the CSS rules to the div inside the cell. </p>
37.How To Style Forms?
Forms and form elements like SELECT, INPUT etc. can be styled with CSS - partially.
Checkboxes and Radiobuttons do not yet accept styles, and Netscape 4.xx has certain issues, but here is a tutorial that explains the application of CSS Styles on Form Elements.
38.Must I quote property values?
Generally no. However, values containing white spaces, e.g. font-family names should be quoted as whitespaces surrounding the font name are ignored and whitespaces inside the font name are converted to a single space, thus font names made up of more than one word (e.g.) 'Times New Roman' are interpreted as three different names: Times, New and Roman.
39.Do any WYSIWYG editors support the creation of Style Sheets? Any text-based HTML editors?
As support for CSS in browsers has matured in the last year, both WYSIWYG and Text-based HTML editors have appeared that allow the creation or the assistance of creating Cascading Style Sheet syntax. There are now at least two dozen editors supporting CSS syntax in some form. The W3C maintains an up-to-date list of these WYSIWYG and text-based editors.
40.To what are partial URLs relative?
Partial URLs are relative to the source of the style sheet. The style sheet source can either be linked or embedded. To which source partial URLs are relative to depends on their occurrence.
If a partial URL occurs in a linked style sheet then it is relative to the linked style sheet. The URL of the linked style sheet is the URL of the directory where the sheet is kept.
If a partial URL occurs in an embedded style sheet then it is relative to the embedded style sheet. The URL of the embedded style sheet is the URL of the HTML document in which the sheet is embedded.
Note that Navigator 4.x treats partial URLs as being relative to the HTML document, regardless of the place where the partial URL occurs. This is a serious bug which forces most authors to use absolute URLs in their CSS.