i was getting the error in my asp.net application like this
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that
i googled it and got 791 results.
i tried every possible solutions but could not solve my problem
then finally i got one solution, tried that and bingo it worked
here is the solution:
this link generates machine key automatically
and also generates codes for web.config file
just copy paste that code in web.config file
and run ur application again.
contact me if u cant solve it