Looks like we got another new feature today. I just noticed that posts are opening as a popup instead of as a new page. That's neat, but I can't see how to go back except by clicking the X (top right). Some other sites use the Escape key to go back.
Edit: Alt-Left also takes you back or click outside the popup. Cannot seem to page down without clicking on the popup first.
BTW I've passed 1000 posts!