My Site's error log is filled with these errors:- This is an invalid script resource request. Invalid viewstate. Invalid character in a Base-64 string. Invalid length for a Base-64 char array. All these errors are appearing at least 100 times a day. After doing some RnD on internet i have done following things:- 1- define machine key in my web config. 2- created robots.txt file and add ScriptResource.axd file in that. Can some one guide me what I am missing or doing wrong.