title: ASP.NET Viewstate validation - ASP.NET 1.1 vs. ASP.NET 3.5
body: <p>we're in the process of migrating our web app from ASP.NET 1.1 to ASP.NET 3.5. Our app runs on multiple servers through DNS round robin, so every browser request may end up on a different server. We do have a  in our web.config to prevent validation errors.</p>
  
  <p>However, our plan was to migrate one server at a time. Now it looks like when a user loads the page on a 1.1. server and then the page ends up on a 3.5 server on postback, the viewstate validation fails.</p>
  
  <p>I haven't been able to find anything on the web regarding this issue - it's just my guess that the viewstate validation is incompatible between 1.1. and 3.5, i.e. a viewstate generated by 1.1 will not validate on 3.5 even with the same machineKey and vice versa.</p>
  
  <p>Can anyone confirm this suspicion?</p>
  
  <p>Thanks</p>