Cascading Style Sheet (CSS)

A cascading style sheet (CSS) is a Web page derived from multiple sources with a defined order of precedence where the definitions of any style element conflict. The Cascading Style Sheet, level 1 (CSS1) recommendation from the World Wide Web Consortium (W3C), which is implemented in the latest versions of the Netscape and Microsoft Web browsers, specifies the possible style sheets or statements that may determine how a given element is presented in a Web page.

CSS gives more control over the appearance of a Web page to the page creator than to the browser designer or the viewer. With CSS, the sources of style definition for a given document element are in this order of precedence:

1.      The STYLE attribute on an individual element tag

2.      The STYLE element that defines a specific style sheet containing style declarations or a LINK element that links to a separate document containing the STYLE element. In a Web page, the STYLE element is placed between the TITLE statement and the BODY statement.

3.      An imported style sheet, using the CSS @import notation to automatically import and merge an external style sheet with the current style sheet

4.      Style attributes specified by the viewer to the browser

5.      The default style sheet assumed by the browser

In general, the Web page creator's style sheet takes precedence, but it's recommended that browsers provide ways for the viewer to override the style attributes in some respects. Since it's likely that different browsers will choose to implement CSS1 somewhat differently, the Web page creator must test the page with different browsers.

CSS can be divided into 3 types:

They are:

1. Inline CSS

2. Internal CSS

3. External CSS

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Browser

A browser is an application program that provides a way to look at and interact with all the information on the World Wide Web. The word "browser" seems to have originated prior to the Web as a generic term for user interfaces that let you browse (navigate through and read) text files online.

Technically, a Web browser is a client program that uses HTTP (Hypertext Transfer Protocol) to make requests of Web servers throughout the Internet on behalf of the browser user. Most browsers support e-mail and the File Transfer Protocol (FTP) but a Web browser is not required for those Internet protocols and more specialized client programs are more popular.

The first Web browser, called WorldWideWeb, was created in 1990. That browser's name was changed to Nexus to avoid confusion with the developing information space known as the World Wide Web. The first Web browser with a graphical user interface was Mosaic, which appeared in 1993. Many of the user interface features in Mosaic went into NetscapeNavigator. Microsoft followed with its Internet Explorer (IE).

As of September 2006, Internet Explorer is the most commonly used browser, having won the so-called browser wars between IE and Netscape. Other browsers include:

·         Firefox, which was developed from Mozilla (the open source version of Netscape).

·         Flock, an open source browser based on Firefox and optimized for Web 2.0 features such as blogging and social bookmarking .

·         Safari, a browser for Apple computers (at this writing, the third most popular browser).

·         Lynx, a text-only browser for UNIX shell and VMS users.

·         Opera, a fast and stable browser that's compatible with most relatively operating systems.

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