ASP.NET authentification session

Question

i have many sites under one asp.net forms authentification, they have mixed frameworks, some have 2.0 some 4.0. but it is all fine. everything works fine. but!!

here part of my web.config:

<authentication mode="Forms" ><forms loginUrl="../web/start_page/start_page.aspx"
    name=".ASPXFORMSAUTH" 
    protection="All"  
    path="/" 
    timeout="60" /></authentication>  
<machineKey
  validationKey="blablabla"
  validation="SHA1" />
<sessionState mode="InProc" stateNetworkTimeout="3600" />

Sometimes, after random time, for example two minutes, session on client ends, and he has again to enter password, why?? what am i missing?

Event Viewer shows:

Event code: 4005 
Event message: Forms authentication failed for the request. Reason: The ticket supplied    has expired. 
Event time: 21.09.2010 8:23:26 
Event time (UTC): 21.09.2010 4:23:26 
Event ID: e3a00bef332a4dec9cd1aa078a3d5aa4 
Event sequence: 277 
Event occurrence: 1 
Event detail code: 50202 

Answer 1

its because session time out event occurs so you need to increase your session time something like this

<configuration>
  <sessionstate 
      mode="inproc"
      cookieless="false" 
      timeout="20" 
      sqlconnectionstring="data source=127.0.0.1;user id=<user id>;password=<password>"
      server="127.0.0.1" 
      port="42424" 
  />
</configuration>

Timeout. This option controls the length of time a session is considered valid. The session timeout is a sliding value; on each request the timeout period is set to the current time plus the timeout value