I have a 11 website with the same code with only different data, I copy the same website in sub domain of the original website, Different data come from id for every website in dataaccess, the code always work right but sometimes when some pages like " register or login" cause a error page
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
i work with framework 4
This is because of shared webhosting. Please check below useful links
Asp.net Validation of viewstate MAC failed [Stackoverflow]