CSS Interview Questions and Answers -03

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.

What are the advantages/disadvantages of the various style methods? 
External Style Sheets
Advantages

* Can control styles for multiple documents at once
* Classes can be created for use on multiple HTML element types in many documents
* Selector and grouping methods can be used to apply styles under complex contexts

Disadvantages

* An extra download is required to import style information for each document
* The rendering of the document may be delayed until the external style sheet is loaded
* Becomes slightly unwieldy for small quantities of style definitions

Embedded Style Sheets
Advantages

* Classes can be created for use on multiple tag types in the document
* Selector and grouping methods can be used to apply styles under complex contexts
* No additional downloads necessary to receive style information

Disadvantages

* This method can not control styles for multiple documents at once

Inline Styles
Advantages

* Useful for small quantities of style definitions
* Can override other style specification methods at the local level so only exceptions need to be listed in conjunction with other style methods

Disadvantages

* Does not distance style information from content (a main goal of SGML/HTML)
* Can not control styles for multiple documents at once
* Author can not create or control classes of elements to control multiple element types within the document
* Selector grouping methods can not be used to create complex element addressing scenarios

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>

What is imported Style Sheet? How to link?
Imported Style Sheet is a sheet that can be imported to (combined with) another sheet. This allows creating one main sheet containing declarations that apply to the whole site and partial sheets containing declarations that apply to specific elements (or documents) that may require additional styling. By importing partial sheets to the main sheet a number of sources can be combined into one.
To import a style sheet or style sheets include the @import notation or notations in the STYLE element. The @import notations must come before any other declaration. If more than one sheet is imported they will cascade in order they are imported – the last imported sheet will override the next last; the next last will override the second last, and so on. If the imported style is in conflict with the rules declared in the main sheet then it will be overridden.

<LINK REL=STYLESHEET HREF=”main.css” TYPE=”text/css”>
<STYLE TYPE=”text=css”>
<!–
@import url(http://www.and.so.on.partial1.css);
@import url(http://www.and.so.on.partial2.css);
…. other statements
–>
</STYLE>

What is a Style Sheet? 
Style sheets are the way that standards-compliant Web designers define the layout, look-and-feel, and design of their pages. They are called Cascading Style Sheets or CSS. With style sheets, a designer can define many aspects of a Web page:

* fonts
* colors
* layout
* positioning
* imagery
* accessibility

Style sheets give you a lot of power to define how your pages will look. And another great thing about them is that style sheets make it really easy to update your pages when you want to make a new design. Simply load in a new style sheet onto your pages and you’re done.

What is alternate Style Sheet? How to link? 
Alternate Style Sheet is a sheet defining an alternate style to be used in place of style(s) declared as persistent and/or preferred .
Persistent style is a default style that applies when style sheets are enabled but can disabled in favor of an alternate style, e.g.:

<LINK REL=Stylesheet HREF=”style.css” TYPE=”text/css”>

Preferred style is a default style that applies automatically and is declared by setting the TITLE attribute to the LINK element. There can only be one preferred style, e.g.:

<LINK REL=Stylesheet HREF=”style2.css” TYPE=”text/css” TITLE=”appropriate style description”>

Alternate style gives an user the choice of selecting an alternative style – a very convenient way of specifying a media dependent style. Note: Each group of alternate styles must have unique TITLE, e.g.:

<LINK REL=”Alternate Stylesheet” HREF=”style3.css” TYPE=”text/css” TITLE=”appropriate style description” MEDIA=screen>
<LINK REL=”Alternate Stylesheet” HREF=”style4.css” TYPE=”text/css” TITLE=”appropriate style description” MEDIA=print>

Alternate stylesheet are not yet supported.

How can you set a minimum width for IE? 
To set a minimum width, the CSS property is ‘min-width’. This can be very useful and works well in good browsers. IE doesn’t understand ‘min-width’. However, it has a proprietary property called ‘expression’ which allows us to feed it javascript via a stylesheet. Below is how to set a (780px) minimum width for IE…

<!–[if gte IE 5]> <style type=”text/css”>
body {
width:expression(documentElement.clientWidth < 780 ? (documentElement.clientWidth == 0 ? (body.clientWidth < 780 ? “780px” : “auto”) : “780px”) : “auto” );
}
</style>
<![endif]–>

As the property is non-standard, it won’t validate with the W3C validator, so if we put it in the head like this (above) – in an IE conditional comment – the validator will ignore it and the page will get a clean bill of health.

Which browsers support CSS? 
It depends on your definition of “support.” If you are interested in those browsers which makes some attempt at supporting CSS, no matter how partial or bug-ridden, then the list is:

* Internet Explorer 3.0 and above
* Navigator 4.0 and above
* Opera 3.6 and above
* Konqueror
* Arena
* Emacs-w3
* Amaya
* Lexicon
* XPublish by Media Design in·Progress

If instead you’re interested in those browsers which are known to do a credible job of bug-free and mostly completel support for CSS1, then the list narrows somewhat dramatically:

* Internet Explorer 5.0 for Macintosh and above
* Internet Exporer 5.5 for Windows and above
* Netscape Navigator 6.0 and above
* Opera 4.0 and above

While none of these browser can be claimed to have a perfect implementation of CSS1, they are all quite good and can be relied upon to operate in a consistent fashion for most of CSS1.