Key

Image - Announcement
Image - Sticky thread
Image - Topic you've read
Image - Unread Topic
Image - Topic that you have posted in, with no unread posts
Image - Topic that you have posted in, with unread posts
Image - Hot topic
Image - Locked thread
Image - Moved thread
Image - Forum with subforums (which have been read)
Image - Forum with subforums (which are unread)
Image - Link forum