error mesage

Hello, I'm student from Czech Republic and I writing web pages like school  
activity.
My pages have been valid, but yesterday the W3C validator found a mistake,  
which I don't know, where is it and how can I fixed it.
The results of my validation of the web pages are here:  
http://lide.gymcheb.cz/~mikrbec/oktava/seminarka-VOS/index.php; I think  
the error is with you.
Thank you

Michal Krbec, Gymnasium Cheb, Czech rep.

NOTE: Whenever possible, give the address of the document you were  
checking.
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Received on Wednesday, 3 March 2010 11:54:06 UTC