Blueprint is a comprehensive CSS framework that aims to simplify your web development projects.
You get an easy-to-use grid that's up to handling even the most complex layouts, for instance. While a CSS reset eliminates browser discrepancies, allowing you to concentrate on your design.
There are bundled themes and frameworks to help you get started with Drupal, Wordpress, Mediawiki, dotnetnuke and more. And a core set of plugins add support for fancy type, column layouts, buttons, and link icons.
You also get high quality typography, excellent form and print styles, and a range of tools, editors and templates to help you along the way. You're a web novice? Then this may be a bit much, and you will need to spend time learning the basics, but don't panic - there are plenty of tutorials and demos to explain what's going on.
Blueprint is a very flexible CSS framework, and relatively easy to use (though if you're a CSS beginner you'll still be spending a long time with the tutorials)