"Server Error in '/' Application" In Asp.net Problem

Error message:
“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

There problem is mainly occur by the Wrong Asp.net configuration.

For configure Asp.net properly you need to loging the plesk control Panel.

click Asp.net select Authentication as forum. Normally it is set default as

windows.

Error message description
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: 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.

Source Error:

The source code that generated this unhandled exception can only be shown when compiled in debug mode.