Using CSS to style semantically meaningful (X)HTML markup is an important key to modern web design practices. In a prefect world, every browser would interpret and apply all CSS rules in exactly the same way. However, in the imperfect world in which we live, quite the opposite frequently happens to be the case: many CSS styles are displayed differently in virtually every browser.

Many, if not all, major modern browsers (e.g., Firefox, Opera, Internet Explorer, Netscape, et al) implement their own generalized CSS rules, which often conflict with designer-applied styles. Other browsers fail to implement properly various CSS rules, making a mess of pages that happen to display perfectly in other browsers. Even worse, some browsers completely ignore specific aspects of CSS altogether, entirely ignoring widely accepted CSS attributes and properties. ......