Re-learning CSS the right way

Check out Designing With Web Standards by Jeffrey Zeldman.

Here are some general rules to live by:

• Tables are good for tabular data. If the data you're presenting belongs in a table, don't go out of your way trying to make a grid out of <div>s. Doesn't make sense.
• As far as layout is concerned, use <div> tags, stay away from tables. Get to know the float property well. With CSS3, there are going to be new, improve standards to the display property. Learn them.
• display: none completely removes the element from the viewport. Conversely, visibility: hidden retains the whitespace that the element would have otherwise taken up. In both cases, the element remains in the DOM.
• General rule of classes and IDs. Page elements and IDs should have a one-to-one relationship per page. For example, #Column1, #Column2, #Footer, #Header. Page elements and classes, on the other hand, should be a many-to-one relationship, like: .container or .navLink. Use classes when you know you're going to be using a particular element quite a bit.
• Think in terms of efficiency. The less style rules you have, the more quickly your page will load and the easier style issues will be to debug.

I have about a million other things to say but that should get you started.