What is "Who's Online" and why can't I see it?

The "Who's Online" page can tell you who is online at that time, their Location (what page they are viewing), and when their last activity was (in case the person went off, but left the page up). It can only be viewed by those who have made a certain number of posts. In order to see "Who's Online", you will need to meet this post count. However, this is not an invitation to SPAM (or post Short, Pointless, Annoying Messages), which is against Site Guidelines.