I didn't say I was actually reading all of them... :-) I'm quite sure now that my guess is right. Let's say you enter the first page at 10am and read until 10:15. If you "Mark All Read" you will see all new posts between 10 - 10:15. If you replied/posted while this page was visible, your own submission clearly falls in this same period. However, if you hit "Next" at 10:15, then your second page gets "10:15" as a new beginning, and if you hit "Mark All Read" at 10:30 from the second page, you will see the new bits between 10:15 - 10:30, but you will miss the ones between 10 - 10:15. That's why it might be a good idea to leave the first page open (and untouched) and browse the rest in a separate window. Let's say you enter page umpfteen at 12:30 and read until 12:35. If you hit "Mark All Read" there, you would only save the bits between 12:30 - 12:35 but miss 10 - 12:30, but if you do it in the first page/window, it should still use "10am" and you should see everything between 10 - 12:35 as "new". Confusing, eh!? :-)