Sir,

 I have Repeater control on page and binded it dynamically from database. When I click on link button it showing me an error as 

Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

I have searched on google and got the solution as to add  EnableEventValidation="true" ViewStateEncryptionMode="Always" EnableViewStateMac="true" at top. I have done but still getting same error...