Read posts don't disppear from Unread Posts list


Previously, browsing the unread posts list, whenever I pressed the Back button the list refreshed (i.e. the post I just read disappeared from the list).

This morning (using a different computer, if it might be relevant) the threads are almost always still there.

Also, when tinkering with the filter (switching from showing posts up to 2 days old back to show all posts), I got an Error page:

"Server Error in '/forum' Application.

Validation of viewstate MAC failed"

PS Having posted the above, I wanted to change the font back to whatever the standard font/size is, to type this bit.  Unfortunately, I can’t tell what the standard font is, because highlighting a patch of standard font doesn’t make anything appear in the “Font Family” or “Font Size” pop-down windows.  (By contrast, if you highlight the red text above, it helpfully shows Verdana, 18 point and Bold.)