Follow one of these options to solve the problem: Host your site on a server where the application pools never recycle! Certainly, this is impossible in Shared Hostings. You need a VPS server or dedicated server, where you can configure your own settings. Disable View state Mac , just run “enableViewStateMac=”false“” in your web.config on Pages tag under system.web tag. Please note that this step is not 100% secure “and NOT recommended”. Configure ASP.NET to not use Auto-Generated Key but rather a predefined key. This is the perfect and secure method . Generate your key by yourself using Windows Shell.