Clarification regarding Forum Icons pleas

[HHGT]

When I hit the "New Posts" link I get a list that displays envelope icons on the left side of the screen that are either Red or Gray and sometimes with a Green arrow pointing left and sometimes without. What do they mean?

Also, it seems that if you click on the "New Posts" link after replying to one or many posts, the page gets refreshed and seems to omit unviewed threads. Any one else notice this or am I doing something wrong?

 

[2112]

I think the green arrow means you are subscribed (with a post?).

I don't get the omitting of threads, if I understand you correctly. The unviewed stay bold. Now if I leave the computer unattended for a while, I will loose all the unviewed threads.