MMO-Champion is the biggest news website of World of Warcraft. The main page is viewed millions times a month and was done with old school tables. As a result, it was really slow to load but worse, all the content had to be loaded before being displayed.
The first thing I did was to rewrite the whole main page template using clean and valid HTML + CSS. The goal was to make it compatible up to IE6. The rendering was so much pixel perfect that nobody noticed a change when we pushed it live.
The main challenge was to rewrite the menu. Previously, the menu was using several images that were cut in order to make it easy to implement it in CSS. However, it was a torture to add another menu. The new one is now using a single image that is basically a screenshot of the rendered menu.
In order to save bandwidth, if the browser is supporting HTML5, instead of storing the menu state in a cookie, it is saved under the new localStorage feature.