Error : Validation of viewstate MAC failed

If you get the error following error in your .NET app -

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.

Please follow these instructions to resolve it.

Visit http://aspnetresources.com/tools/machineKey and generate a machine key.

Place the key into your web.config within the  node (do not use the key below) e.g.

validationKey='2EEA416CEFC6D6BE856ED57B97FB9CA7DFA CE17C073125949A1D682C80A44BB2A
D887DDDC13DBFB0954F1000FEE5757E99693F222F8E28CAA2E 6DAB8C4F99E0C'
decryptionKey='877478B2F33A74226ABEF55FDCC1A76E43F 1BBEA6241A592'
validation='SHA1' />

Close your browser and reload your website to test.

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