Hi Pawan,
In general clicking on the cancel button cancels the request to the server with the notable exception of uploading files in IE6/7/8/9. In those versions of IE it is not possible to cancel the upload once sent to the server.
On a side note what do you do in your custom handler so that it hangs the server? Perhaps there is a way to optimize that functionality so that it doesn't cause freezes.
Regards,
Genady Sergeev
Telerik
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