hi! i don't know if this is a limitation or might be something else but when i opt for viewing topics i replied to ... then reading on 1 ... then opting to go back (hitting Back) to the same index (where it displays all the topics i replied to), it always tells me that page has expired ... & i always have to refresh the page ... is it really like this? thanks!

It is expected behavior in web pages. Not just MSFN. It is a result of a form POST.

thanks jcarle! it's just that it doesn't happen while viewing all posts then hitting back ...

Depends on the method used to send you to the new page. If you were sent by a GET response, then you won't have that, but if you were send with a POST response, it'll happen.