If it's that there is a thread you don't really care about anymore (if the discussion has gone in a direction you don't care for), go under "thread tools" at the top of the page in the thread, and you can unsubscribe, which will take it off the list.
Edited to remove information that was patently untrue. I am of less help in this area than I thought. Different settings for different forums and all.
so when you go to the new replies button at the top there's no way to mark those read. They used to be marked read when you read them and they would disapear from the list but now they don't. will this change.