Expired login session - cookie issue?
 

This feels like such a newbie question...

I notice that for one of the forums I'm working to launch, I'll get logged out and have to re-enter my username and password after the cookie timeout I've set - but on other sites this doesn't happen, including one of my other forums, this site, vb.org, among others. On the other sites, I just navigate to the site and I'm recognized; no need to log in.

I'm thinking there's gotta be a setting somewhere that I'm just failing to find.

Are there one or two obvious things I should check?