As I mentioned before, I dont think this problem is related directly to this mod. Try to uninstall this mod (at least undo Step 1, 2 and 3 - asuming you see this problem on index.php, if not undo the changes in the file where the problem is)
Second, I see no such problem on your site neither in IE nor in FF.
But, I've noticed another thing that only showed in FF: there are some characters showed on top of each page. . I've experienced such myself in the past, and it turned out caused by my php editor that saved files in Unicode (UTF-8) encoding and added "BOM" identifications at the beginning of each file. Normaly any editor that supports Unicode/UTF8 does not show these characters, but PHP seems to treat them as a plane text and send them to the browser as plain text.
So, make sure you save your files in 8-bit ecoding (ISO) and not in unicode.
P.S. if you copy text from a web page that uses Unicode or UTF-8 and then paste it into notepad/wordpad and save it, it will save the file in Unicode or UTF-8 encoding.