query ref ie7 and wordpress

On my website, on the following page:

http://www.i3pep.org/sitemap.php

I recently found out, that in ie7, the “text block” on the left containing “Article Categories” become invisible.

• Can someone tell me if its ie7 problem, or something to do with css or some coding problem?

The text block is visible in other browsers and the similar text blocks are visible in ie7 on other pages

also tested on browsershot:
http://browsershots.org/website/http://www.i3pep.org/sitemap.php