</div> tag after </html> doesn’t let me validate my website

Hi,

I’m trying to validate my website and the only error i’m getting is a very strange error:
i have all the tags opened and closed in the right way, but at the end of the page some script i don’t know, adds a </div> (which go after the </html> tag), so the validator gives me the error that can’t be a tag there.

Any of you know how to debug it? Which function to check? which php function to search for? I’m stuck with this. I would appreciate also if someone can suggest me a good tool that said me from which php file comes that line.

If you want to take a look the website is http://www.osioaperta.it

Thanks, i hope in your answer cause i don’t know what to do.