I ran into an issue where a web application threw a System.Web.HttpException in Firefox with this message:

The state information is invalid for this page and might be corrupted.

It was reproducible with a specific sequence: do something on the page that causes a postback, use the browser's back button to return to the previous page, use the refresh button, then click a button to cause another postback.

The cause is the combination of ViewState and form autocomplete. On refresh, Firefox restores the form fields to the values the user had entered, including the hidden ViewState field. The restored ViewState no longer matches what the server expects, and the postback fails.

In my case the fix was turning autocomplete off at the form level:

<form id="form1" autocomplete="off" runat="server">
    ...
</form>

You can also set autocomplete="off" on individual inputs if you do not want to disable it for the whole form. Worth noting that turning it off at the form level also stops the browser from offering to save and fill legitimate fields, so it is a tradeoff rather than a free fix.