We have a website that is getting a "Validation of viewstate MAC Failed. If this application is hosted by a Web Farm or Cluster...." error.
The website was created in VS2005 and .Net Framework = 2.0.
It seems that if the user spends a long time on the website without doing anything and then tries to do something this error message is displayed.
I also have this happening on another website which is VS2008 with .Net Framework 3.5
How do I get around this error?