CSS Floats are critical
Until IE comes out of the dark ages and begins supporting css2.1, the float property will remain the most powerful and the most flexible layout tool we have.
The Gotchas will getcha
The css float, along with position are easily the least understood of all properties. It doesn't take but a few run-ins with relative and absolute positioning to bring yourself up to snuff. In a nutshell, AP elements are completely out of the flow, while RP elements are in the flow and their shifted contents are out.
… are neither fish nor fowl nor good
red meat. They are completely out of the flow, but
inline elements are aware of them, and block elements
are not. IE’s feature-full/buggy—I don't
know what Microsoft was thinking—hasLayout has caused many developers
hours of anguish as IE’s float model
refused to work as advertised.
In this section we shall demonstrate how floats are supposed to work, and how to deal with IE without breaking things for modern browsers.