With their many useful applications, cascading style sheets are a web designer's friend. Definitions for layout, type, fonts and colours can be set in one document and applied to your entire website.
When you need something globally, across many pages of your site, you simply update one cascading style sheet (CSS) and it affects all the pages using that style - much easier than having to mess around updating font tags in HTML pages.
CSS removes the shackles of HTML formatting. In Dreamweaver, it's easy to master and will give you enough creative freedom to produce rich and vibrant websites.