I've written a web site that uses IIS Forms Authentication. It's configured to use authentication tickets with a sliding expiration. FireFox allows the ticket to expire while it works fine with Internet Explorer. The web site uses a Keep Alive page that uses the meta refresh tag to periodically post back to the server to keep authenticated. This is done because some users have a need to use another web site that does not run in IIS and we don't want their authentication to time out while they are there. I used Fiddler to monitor the requests and responses and found that when IIS sends the updated cookie with the authentication ticket containing the revised expiration date, the cookie appears to be accepted by FireFox (according to CookieSafe as recorded in the error console Ctrl-shift-J). When the meta refresh occurs, the browser sends the original request with the obsolete cookie. This keeps occurring until the expiration time is up on the ticket. IIS keeps sending new cookies but they seem to be ignored. IE, on the other hand, accepts the cookie and you see it in the next request for the keep alive page. I figure it might be related to caching, but I think I disabled that and it still does it. I'm going to try adding a random code to the KeepAlive url but I can't see why that should matter. Why wouldn't FireFox send the cookies as the values are set? I'm hoping this can be fixed with a simple config change.