Although this is a PHP forum and your problem is HTML I'll give you the answer as I see it ;)
At the bottom of your forum you have a small dropdown box that allows you to jump around to different places or maybe to change skins (I'm not sure because I don't speak the language)
Obviously for this to work it must be in a form. However, your problem is that there is no closing of the form tag. For example you have
The main reason you can't find it is that the output is not very clean. No newlines no indentions, in a lot of cases just code. This could be because of the software you are using and how they do templating.
I'll give you exactly what to search for in your file and then you can change it.
Open up your template file (particularly the one for your darkx skin) and search for this HTML