CSS;

CSS is a set of formatting instructions that controls the looks of a web page or pages. CSS stands for Cascading Style Sheets.  Some browsers that support CSS is: (Firefox,IE3 or later, NN4 or later). May be saying, great this will definitely save me some time.  You also need to know that though, the majority of the browsers understand CSS, they do not fully support all of it's capabilities.

HTML is EXtensible HyperText Markup Language. XHTML Is HTML with stricter rules-that adds conformity and, is 99% XML compliant. So you should be familiar with or become lot of comfortable with HTML, XHTML, and the style properties of Css. But anything on the Internet, Css can be used for the bad and the Good. I think  Obviously, if you want to keep your site up on the Google rank and running for a long time, Sometime CSS techniques should be avoided. Why? Because many CSS techniques be considered spam by the search engines. The blackhat tactics include such things as: 1); hiding and bolding or italicizing copy for search engine spiders benefit only. 2) using CSS to hide text-from headlines to body from the human eye.

CSS is a viable way to making your web pages easier to maintain-if the majority of your pages follow the Othes techniques and format. If you are not all that familiar with CSS, then take the some time to look at w3schools.com tutorial. It's very nice information and can get you started with CSS.