Well Pilfo, you do have accessibility problems.
Before going into the usability details, I suggest you to check the following issues, I have found, ckecking the code of your homepage (index.html):
1. You did not identify the language of your text.
HowTo: http://bobby.watchfire.com/bobby/html/en/gls/g125.html
Line 19, 21, 22: "Frame" elements require the "title" attribute to facilitate frame identification and navigation. Frame titles must be meaningful. For example, "Table of Contents", "Where the content is displayed", and "Sitewide navigation bar" (or simply "Navigation").
HowTo: http://www.hisoftware.com/uaen/WebHelp/uaen.htm or
http://bobby.watchfire.com/bobby/html/en/gls/g39.html
When you fix these issues, let me know, and we can go on checking the other pages of your web site.