It's in random screens -happens about 30-40% yes/60-70% no.
Just now as a 'test', I clicked on Nutrition & Health -- and then Chea's lovely thread "Vommit, Diarrhea and Heat Waves, OH MY!"
And when I clicked back (to go back to the Nutrition index, the message below came up). When I hit back on some pages it gives me the same msg and on other pages, it does like it did.... Big Ant explained when I complained about same on PBC that the sites can be set up to either utilize the back feature or not, in which case you have to click the itty bitty "Return to Nutrition & Health" link.... It's sorta intermittent on PBC too but more like 80 yes/20 no.
"Warning: Page has Expired The page you requested was created using information you submitted in a form. This page is no longer available. As a security precaution, Internet Explorer does not automatically resubmit your information for you.
To resubmit your information and view this Web page, click the Refresh button. "