It is this separation that gives style sheets their power. You can change the overall look of an entire page or even entire Web sites by changing one style rule or sheet. Style sheets are engineered with the future in mind. Style sheets' independence of style from structure makes it easier to adapt the Web to different technologies and ways of experiencing those technologies. The idea is that by separating style from structure, either can be changed without affecting the other.
Style sheets use common desktop publishing terminology.
No more crude workarounds for HTML's limitations, style sheets allow designers much more control over the look and layout of their pages. Each HTML page can be influenced by one or more style sheets. Styles rules can be embedded inside a page or referenced in a separate file. Since multiple style sheets can influence the presentation simultaneously conflicts can arise. Conflict resolution is an integral part of the CSS spec, and is based on each style rule having a weight.