I have made a new feature...
When the "New Post" link in the top menu bar turns red it means you have new post that are unread.
Click it and read the posts that interest you but when you are done click the "Mark all topics as read" link in the bottom blue bar. It will mark all topics as read and the red notification will turn off. It will also turn off if you read all the new topics but since some may not be of interest to you the best thing is to click the "Mark all topics as read link"
Notice the link at the bottom right of this graphic:
As a side note to this... the Private Message link will also turn red when you get a new Private Message.