WebApp Sec: Content monitorting in Application Security

[Alfred Hitchcock <alfredhitchcock_007 () yahoo com>]

Hi All,
I have a major doubt it would be of great help if anybody can provide solution to this.
I have a web page which allows to upload files such as jpeg and html files.
Is there any mechanisms which can detect malicious html files. E.g. if a html page has got a malicious java script such 
as alert('xss') then how can we check these things. One more point to be noted here is that uploading of file can be 
done by any user.