The Concept Behind CSS
The concept behind CSS (a.k.a. cascading style sheets or style sheets) is really simple. CSS allows you to make changes to all of the web pages that link to the CSS file at once by changing a style in the style sheet, instead of having to manually change every style in every HTML file.
CSS allows you to create a single document of code, similar to an HTML file, that lets you specify the colors, fonts, backgrounds, etc. of a web page. The CSS file is then linked to from the web page(s) that you want to have the same styles that you specify.
If CSS did this and only this, they would save you a lot of time to say the least, especially if you have a large or multiple web sites. This alone is worth learning CSS, however, style sheets allow you to do this and much more.
CSS also allows you to:
* position text and graphics precisely where you want to
* add rollover effects to links
* control the spacing between letters, lines, margins, web page borders
* specify the units such as centimeters, pixels, points and more
* hide content from certain web browsers in certain situations. An example of this is when you have some content that you want to appear only in your web pages, but not in print.
In the end, CSS can save you a lot of time and effort and is very easy to learn.