A partial list of reasons: uniformity, efficiency, separating style from content, improved usability, long-term planning, pixel-perfect presentation, to do stuff you can't do with plain HTML.

Each person will have their own reason for using CSS styles. They can be tricky to learn, and like any other technology, can become very complicated very fast. That being said, the learning curve starts out gradual, so it's easy to start experimenting without getting overwhelmed. And a tool like Dreamweaver makes it simple to apply and create styles without knowing the knitty-gritty.

Templates and CSS Styles work well together. While templates can provide consistency of the overall layout of webpages on your website, styles can provide consistency in the finer details of presentation. By altering one file, you can alter the display of every page on your website!

An example? Let us say we mark our important section titles in our webpage with "Heading 2" (<h2> tag in HTML). That Heading 2 text will then display according to how the referenced CSS files say it should display. Now, should we ever need to change the color scheme for our website, there is no need to go in and change the color on the many webpages that use <h2> tags. Instead, we only need change the CSS file that all the webpages point to. We change that <h2> definition in the CSS file to bold, 16pt, and Times New Roman, and then like magic all the pages with <h2> defined sections will display in bold, 16pt, Times New Roman font.

To get an idea of the pre-defined SJU styles that are ready to use right away, please see our Sample CSS Styles demo page.

Reference

Non-SJU general documentation, reference, and tutorials on CSS may be found here:

• CSS Tutorial (from w3schools.com)
• Guide to CSS, a beginners Quick Tutorial (from htmlhelp.com)
• Articles on CSS by expert Eric Meyer
• Many more resources (from webreference.com)
• And one more final meta-resource for good measure (from css.nu)

Books:

• Eric Meyer on CSS (by Eric Meyer)
• HTML Utopia: Designing Without Tables Using CSS (by Dan Shafer)
• Many more books (from w3.org)