It’s kind of like asking, "why does gravity suck?"
Reminds me of this pie chart:
You just have to take it one problem at a time. Once you get those errors sorted out, let us know how it goes. It definitely doesn’t guarantee that it will work the way you want it to, but it’s a great place to start.
Yes, this is a common problem in IE6 when making Unordered Lists into horizontal Nav bars. The problem stems not giving a width to the List Item; so it extends 100% in IE6. (Even though the "float" should ignore that width 100%…)
The short cut (manual) fix is to assign a width to each LI.
But that isn’t the only way.. I don’t know exactly the magic item which fixes it, but I’d guess it has something to do with defining a height for the UL so the LI’s have no where to go.
Sorry I don’t have time right now to get the full answer. Here’s the code that’s working on my website. I absolute positioned the UL inside my header which has an assigned height.