When I started I used many on-line tutorials.
HTML and CSS Tutorials, References, and Articles | HTML Dog for instance. But one of the easiest ways I found was to get a copy of image ready. Layout your websites and learn about image map and slices, rollovers etc. Then by dropping these layouts into dreamweaver and golive you can then see the code of how everything is layed out. Then by stripping the code down you can visualize what code the browser it using to display certain web elements. Then you can begin CSS tutorials learning how to repeat certain background images and replacing your pictured text with actual type. It's a gradual process but don't try creating full working, fantastic looking sites straight off it's ok to spend time on basic layouts till you know enough it'll pay off later in your carear. Good Luck.
Study the link on this thread and you'll see how the basic layouts are made by CSS positioning
CSS Layouts - Graphic Design Forum and Web Design Forum.