Error Handling: Catching Errors With ASP.Net and C#

http://www.csharpfriends.com/Articles/getArticle.aspx?articleID=68

Login failed for user 'SQL2K802\Guest'

http://forums.asp.net/t/1409902.aspx

Validation of viewstate MAC failed error

http://blogs.msdn.com/tom/archive/2008/03/14/validation-of-viewstate-mac-failed-error.aspx

Session Expire in 20 minutes or 2 minute

http://forums.asp.net/t/1283350.aspx
http://forums.asp.net/p/1332460/2676515.aspx
http://stackoverflow.com/questions/648992/session-timeout-in-asp-net


1.)http://www.velocityreviews.com/forums/t95194-go-to-login-page-when-session-expires.html

2.)http://zeeshanumardotnet.blogspot.com/2009/01/why-dot-net-sessions-are-cleared-before.html

3.)http://zeeshanumardotnet.blogspot.com/2009/07/why-sessions-are-terminatedloss.html

Validation of Mac failed

http://blogs.msdn.com/tom/archive/2008/03/14/validation-of-viewstate-mac-failed-error.aspx

1.)http://www.andreas-kraus.net/blog/validation-of-viewstate-mac-failed/

2.)http://www.pagedowntech.com/faq/faq.asp?faqid=145

3.)http://www.eukhost.com/forums/f15/fix-validation-viewstate-mac-failed-6085/

sys.webforms.pagerequestmanagerservererrorexception

sys.webforms.pagerequestmanagerservererrorexception ERROR

ok, try another simplest way:

asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="false"
and also setting the EnableEventValidation="false"
======================================================================================
You may want to try setting ValidateRequest="false" in the Page declaration. It worked for me.