Sometimes after you logout you will get an error page Internet explorer cannot display page. This is not a problem with the forum.

Here is the response from YaBB support.

"This is a ISP and Internet problem .. NOT YaBB, doesn't matter what browser .. I'm using FF and get the same can't find the site occasionally, YaBB just supplies the URL the ISP and internet must find and load.  As you could verify, just reloading the URL page (without changes) usually gets you back to the site. "

Clicking refresh will reload the page.