OK - got it (I think) ... still not sure how to make them disappear if I don't respond ... they seem to stay lit up when I go read another topic. I'll experiment. Thanx everyone!

If you you use your Back button to return to the main page, they don't disappear because the page doesn't refresh. Instead use the Index button at the bottom of the last post. This will refresh the page and sort of mark your position on this thread, so when someone else adds to it, your page will show a red 1 again.
DonM