We got strange error last days. ___doPostBack is undefined.
We are building quite advanced website, but not using postbacks much. One of place where postback used is ASP.NET Login Status control.
It is probabalystic, sometimes it is rendered, sometimes - not. For IE, Chrome it works mostly fine, but from FireFox it is quite high chance not to have doPostBack in page source.
PS: In addition, error happens only on live environment, which uses Windows 2003 & IIS 5.0, dotnet framework is 3.5
Can it be because I am using OutputCache on page level?
Yes it might be about the output cache, comment it out and try again please