Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same

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

Solution:
Edit Web.config, and add the line below:
"
<>
< enableviewstatemac="false">
< / system . web>
"or

Edit the page that is getting loaded
<%@ blah....blah..blahh..... enableViewStateMac="False" %>