The Basics of Cascading Style Sheets
Cascading Style Sheets, commonly known as CSS, is a part of the new web standards developed by the W3C. CSS controls all the design elements of a web page, leaving only the code for the page content in the file for any particular page on the internet. By separating these two aspects of web development, many benefits are realized.
Accessibility is a real consideration. Many websites are legally bound to be usable by people with disabilities. Without the use of CSS it is extremely difficult, and most times impossible, for an alternate browser such as a text reader for the vision-impaired to follow the text of the page in a coherent manner. But aside from disabilities, more and more people are using other types of alternate browsers by various wireless devices. Cell phones and PDA's, for instance, both have wireless internet capabilities. Sites designed in CSS, while they will not have the same visual impact, will maintain usability with these devices.
CSS will also help save your web resources. By putting the design elements of your site all in one file you then free the visible pages of your site from those elements, making those files take up less space that you need to have hosted. The smaller file sizes also eliminate the concern of bandwidth usage and in some cases will actually save you money
Probably the best thing about CSS separating the content elements of websites from the visual elements, from a site owner's perspective, would be that once the site is in place, a redesign is usually simply a matter of a redesign. New graphics, rearrange content, change properties of certain elements (colors of links, etc), and your site is brand new again! No need to pay the designer to then go through and apply the new design to every page on the site!
The style sheet with the design elements are then connected to all the content pages and And with each page that is viewed, less that is then connected to the visible pages of your site, you
Because without CSS all of the design elements are right in the page, clouding the content.
which allow web developers to control visual aspects of websites to work the same across various browsers. With CSS comes new techniques and design opportunities that were never possible before. For example, on this site, links that were created with text will display an image after it, once you have visited that link. This is just the tip of the iceberg.

