i notice there are a few icons that are not given in the key at the bottom of a forum, any explaination about what they mean? like a closed greay envelope with a black dot on it, or an open blue envelope with a black dot on it?

i think the black dot means that you have posted in that tread.
the closed envelope means there are no new posts in that thread since your last visit and the open blue envelope means that there are new posts.