Hi, 

i followed the below url  to integrate cutesoft chat with SharePoint 2010. 

http://cutesoft.net/ASP.NET%2BChat/Deployment/CuteChatforSharePoint/Deployment.htm

After completion of step 7, while i publish the masterpage got the below error .

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.

Please do needful. 

Thanks,

balaram.