I've made some pretty substantial changes to the alpha sheets behind the scenes, and to the Pathfinder [Legacy] sheet in particular. Please try clearing your browser cache, or post in the Experimental Features forum if there are any issues!
At this point, we highly recommend that all new Pathfinder sheets be created in the alpha and that existing Pathfinder sheets be copied into it via the 'Copy to Sheets Alpha' link in your regular sheet list
Edit: I have no idea who Gregor Mendeleev is, as the periodic-tables guy was Dmitri Mendeleev. The XKCD comic doesn't mention a first name though, so it still works. You may be confusing him with Gregor Mendel, often hailed as the founder of biology. They were both alive at roughly the same time.