First on all, your site doesn't seems to validate 100% of XHTML.
Also, your Web site doesn't work correctly on IE, so you must have something wrong in your XHTML and/or CSS and/or JavaScript.
Now what you can do is to try to remove your reference to all your CSS file and see if it's work. If it's still doesn't work, remove your JavaScript reference and see if it's work.
If fact, at this step, what you want to know is where the error come from, because if I take your "a href" tag and put it in an empty file, it's work, so your XHTML seems right.
My way to resolve this kind of problem is to reduce the problem at is simple expression. By that I mean, remove all the external factor that can have an impact in my problem.
I hope this will help.
Let me know of your result.