Starting Cascading Style Sheets by stephen cope
Cascading Style Sheets (CSS) are being used more and more by web designers to
layout and format web pages. Although they have been around for several years
now many designers have avoided them due to browser incompatibility.
Although compatibility problems still exist they are no longer an issue for most
applications. Here I will concentrate here on the main features and how they
work and why they are used.
You may find yourself using CSS anyway without you knowing as programs like
FrontPage use CSS (depends on page setup options) for some of their
functionality. <H4>Styles Solve a Common Problem</H4>
HTML was originally designed to define the content of a document but not the
document presentation/layout. The layout of the document was supposed to be
taken care of by the browser, without using any formatting tags. The content is
defined by using tags like h1,
, table, which basically say "This is a header", "This is a paragraph", "This
is a table", by using tags like and so on.
The principal browser vendors, Netscape and Microsoft, competed by adding
support for new, proprietary tags (like the <font> tag and the colour
attribute) and technologies that permitted increasingly high-impact Web pages.
These innovations were good for spurring the development of Web technology, but
they created problems as well.
Consequently it became more and more difficult to create Web sites where the
content of HTML documents was clearly separated from the document's
presentation and that would be displayed correctly on any browser.
The World Wide Web Consortium (W3C) - the consortium responsible for
standardizing HTML - created a language called Cascading Style Sheets, or
CSS.CSS, unlike HTML, is designed solely to define appearance as efficiently as
possible.
It can exist either within HTML or as a linked document, letting developers
separate a Web page's content (marked up in HTML) from its presentation
(defined by CSS). Both Netscape 4.0 and Internet Explorer 4.0 and later support
Cascading Style Sheets.
Style sheets work like templates: you define the style for a particular HTML
element once (e.g. header tag h1), and then use it over and over on any number
of Web pages.
If you want to change how an element looks, you just change the style; the
element automatically changes wherever it appears. (Before CSS, you had to
change the element individually, each time it appeared) .Style sheets let Web
designers quickly create more consistent pages--and more consistent sites.
<H4>How Style sheets are Implemented</H4>
There are 3 basic ways to add the functionality of Style Sheets:
1. Inline - Creating the elements for each HTML Tag. This will allow the
same HTML Tag to have different styles on the same page.
2. Embedding - Creating the elements on the page itself that will affect
every occurrence of an HTML Tag.
3. Linking
- Creating one page that defines the elements and include in the pages that you
want to affect.
For beginners using Embedding or Linking is recommended.. The Linking Style is
used when you want to use the same style on multiple pages, you can then use
Embedding and/or Inline on specific pages that don't fit the design style of
the Linking Sheet. <H4>Precedence and inheritance</H4>
As the term Cascading Style Sheets implies, more than one style sheet can be
used on the same document, with different levels of importance. Generally
styles from different style sheets merge together (cascade) into a virtual
style.
However, If you define conflicting styles for the same HTML element, the
innermost definition--the one closest to the individual tag-wins
The precedence Style Sheets follow is Inline, Embedding, then Linking. Inline
Style takes precedence over Embedding Style, which takes precedence over
Linking Style.
There is a fourth style sheet which is set not by the document author but by the
reader and that is the browser default. Taking this style sheet into
consideration the order of precedence is:
1. Inline Style (inside HTML element) .
2. Embedding Style Sheet (inside the <head> tag).
3. External Style Sheet.
4. Browser default.
So, an inline style (inside an HTML element) has the highest priority, which
means that it will override every style declared inside the <head> tag,
in an external style sheet, and in a browser (a default value).
About the Author
Stephen Cope is a freelance trainer and the Webmaster at -
making a website and Niche
Website Guide.
|
