Click on any of the links and instead of taking you to a new page it's a pop-up page on top of the existing one (plain left click, not middle-click or whatever you have registered to "open in new tab"). Happened a few years back, very annoying. Performance has improved but I remember a few years ago getting a noticeable delay on some pages.

If you don't follow any links (or you open them in new tabs) it does pretty much look like it always has.