Comment on WordPress Nav Menu with Images by SEO Dave.
Go to http://validator.w3.org/ and run your site through the validator. There’s a lot of errors, but most are not a problem (all the Facebook code doesn’t validate, but it doesn’t break anything), what tends to cause problems is HTML tags that aren’t closed, usually it’s div tags not closed.
Load your site in Firefox and click View Source, this will give you access to the HTML output of the page, as you scroll down you’ll note a lot of code is highlighted red as you get closer to the bottom, this means there’s code errors that are probably serious.
The code errors start at the end of the right sidebar code which suggests a widget added to the right sidebar has HTML errors. Looks like it might be the Hits til Now widget, there’s an HTML error in the table code, the closing table tag looks like this:
Surprised that’s broken the sidebar, but fix that and see what happens.