I was lucky enough in getting a chance to solve certain browser compatibility issues in UI design of a certain web project. The problem is, they are using "div" tags to hold content, but these tags are not styled properly with CSS. As most of the UI designers (who, like me, are addicted to UI Design tools) do, I too suggested using tables to align content. But the customer preferred having divs to tables. Neither of us were wrong in our choice, yet I agreed to work using divs (as it's an area which I loved to explore). Here is an excellent article on the choice of using Divs or Tables.
The real challenge came while nesting divs simulating a tabular look and feel. The flow of elements in the page by floating and positioning divs appeared to a big mystery. I googled a lot and found excellent stuff on Understanding Page Layout using CSS at HTMLDog.com. A detailed and very good description of using floats to align your content is given here. This will surely be useful for budding web developers. Hopefully, I should be able to give a solution to the problem by 2moro EOD after reading all this stuff :)