Data save at localhost but on live server exception!

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C#

ASP

hi,
i have form in asp.net page for booking inquiry and data is saved successfully but when i used this in live server the following exception is shown:-

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.

also i have made change in the web.config for viewstate validation to false.
but this message is still their what is the region behind this i don't know
please help me.
So that the website run properly.
Thanks
BALWANT.