Can only consider this as a note to my self since it's all over the internet already.
Session expires very quickly for Sitecore websites. Like only 1 minute.
Cause and solution:
In config file:
Robots' session timeout is set to 1 minute
is not in website layout causing all visitors to be considered as robots.
For Sitecore MVC, please check asp.net mvc - Sitecore 7.5 MVC and HttpContext.Session.Timeout set to 1 min - Stack Overflow out.
While searching for this issue, I came across something that has always been bothering us, it's the CMS editor's session expires quickly. The message
The operation could not be completed. Your session may have been lost due to a timeout or a server failure. Please try again.
shows up always when I try to select images or files. For this issue, sitecore actually has a patch, please go Session timeout when saving Rich Text fieldsto check it out.
For actually the places to set the session timeout for sitecore, please Google, there're plenty out there.