Cascading style sheets (CSS) offer a way to format HTML documents. One major advantage is they let you specify styles in one (or more) documents that can be used in many other documents. For example, you can specify a class of text "my_text" in the CSS document and you can say that you want it to be bold and italicized. Then, you can use a tag like: <font class="my_text>blah</font> and any text in that block will be bold and italicized. If you then change your mind and only want it to be bold, you only need to change the style sheet, and the change will then take effect on any text that you labeled as "my_text" across all of your pages that share that style sheet. CSS instructions may also be placed directly in a document, if you prefer, in which case they will only apply to that document. You may also use CSS to override default styles of HTML elements. For instance, you can override the <h1> tag, so all text within <h1> tags on your site will be changed to the new style you created. They also allow much better precision in object placement than HTML because they will allow you to specify, using horizontal and vertical pixel counts, the exact position you want to put something. In the "old days" of HTML, everything had to be positioned using tables, which was something of a hack. Currently CSS is widely used for search engine optimization because it allows you to keep your keyword-rich text near the top of an HTML source file (so search engines can find it easily), while placing it wherever you want on the actual page as it is seen by a user.

Cascading Style Sheets were originally designed to fill a niche originally not filled by HTML. HTML was originally created for structuring content on webpages (such as headings, paragraphs, ordered and unordered lists, etc). CSS was originally created for designing content on webpages (font faces, colour and size, element position, margins, padding and borders; etc). In the now defunct "Browser Wars" browser manufacturers implemented proprietary tags and tag attributes, many of which were not keeping with the standards that had been developed. As such, CSS became nothing more than a way to fancify text and optimise search engine placement. At the turn of the century, a movement gained momentum that saw more designers design for web standards rather than web browsers. It also saw some less known browser supporting web standards. With Netscape's switch to 6.0 in 2001, Netscape became the most popular browser to support web standards and the other popular browsers followed suit. Since then, the other popular browsers began to support web standards and the browser war came to a halt. Now, by using HTML for structure and CSS for design, web designers can not only ensure that their websites display correctly in newer browsers, but that their website's content is still accessible in all other browsers. For more information on CSS, visit http://www.w3.org/Style/CSS/