I meant the post number you enter in the “jump to” pop-up when you
hit the # key.
Example: I enter a category, select a thread and press #. and enter 123 to
jump to post 123 in that thread.
When i’ve finished reading that thread i leave that category and continue
browsing other threads in other categories.
If i later go back to the first category and thread, when i press # the pop-up
will still contain 123. 
If i now close my browser, the next time i visit that site, the jump to pop-up
will be reset to null. 
In my case, the thread contains puzzles. A puzzle is posed, and users
attempt to answer it. When it has been solved, a new one is posed.
I just want to be able to keep the latest puzzle post number in the “jump to”
so i can just press #Return to return and review it
from any pont in the discussion.
I guess it’s not going to happen any time, as other solutions are available.