Why AsyncFileUpload with Firefox script busy?

See more:

ASP.NET

Javascript

Ajax

C#3.5

A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can

continue to see if the script will complete.

Script: http://localhost:39064/PostanAd.aspx?

_TSM_HiddenField_=ctl00_ScriptManager2_HiddenField&_TSM_CombinedScripts_=%3b%3bAjaxControlToolkit%2c+Version

%3d3.5.51116.0%2c+Culture%3dneutral%2c+PublicKeyToken%3d28f01b0e84b6d53e%3aen-US%3a2a06c7e2-728e-4b15-83d6-

9b269fb7261e%3ade1feab2%3af9cec9bc%3ae4bd8421:12

How to resolve this problem?

In chrome browser properly running, but in firefox browser getting this error.