The first problem I see is that you're still bothering to support IE4 - that's basically been extinct since 2009.
There are multiple issues the HTML, JavaScript, and PHP code. There are <body> and <html> elements in the middle of the page, multiple elements with the same ID attribute, there is a missing " in the dynamically generated links (on the live site, though not in the code you posted). Both IE and FireFox complain about jQuery-related errors (most notably, neither know what '$' refers to). With all those problems, whether any part of it works or not is down more to chance than design. Even if they aren't the cause of the problem, they do nothing to make it easier to find what is.
As I said, there are PHP issues as well, but they wouldn't affect client-side activity.