PHP CSS integration problem

[londes]

Here is the page for reference: http://www.londes.com/aa
I have that website I am figuring out right now divided into three seperate pages using PHP, header, data section, and a footer. The drop-down menu's are in the header. The header can be viewed at http://www.londes.com/aa/header.php.

The header page appears to work properly. However, whenever the header loads on any of the main data frames, the drop-down menu's stop working where the main data page starts (try clicking some of the bottom links on one of the pages). I don't really know how to fix this.
Also, the drop down menu uses button's html programming with <li> and what not, which is affected by the CSS programming. However, I also use buttons on the main part of the website, so the CSS screws that up. Is there any easy way to fix that? Can I somehow rename the <li> so it works properly. One of the pages that you can see doesn't work with a bulleted list is: http://londes.com/aa/products/autodiscounts.php.

Thanks, and if you have any advice or questions you can e-mail me at ulrichlondes2@yahoo.com or IM me at 'mlondes'.