<system.web>
<authentication mode="Forms">
<forms timeout="50"/>
</authentication>
<sessionstate timeout="60" />
</system.web>
<authentication mode="Forms">
<forms loginUrl="Default.aspx" protection="All" timeout="60" name="" path="/" requireSSL="false" slidingExpiration="true" defaultUrl="Home/Default.aspx" cookieless="UseDeviceProfile" enableCrossAppRedirects="false">
</forms>
</authentication>
try this link