Internet Explorer 6 and below often does have a lot of bugs when it comes to building websites, and often small CSS hacks can sort this.
For instance Internet Explorer does not follow the CSS box model yet, and also Internet Explorer 6 and below don't display png files correctly without a png fix for Internet Explorer.
I thought I had a png fix, but looking at Internet Explorer 6 - maybe I don't. I will add this file in later today.