There is a bug occurring on both the Puzzling main site and meta, as you scroll down instead of grading, the background repeats:
Don't know if this is site specific (this is on puzzling), though others have suggested so as we are the only ones with a graded background.
I'm on Chrome, haven't tested other browsers.
A couple of others have said in chat its happening to them too, one after he reloaded the page, so I don't know if there has been any work behind the scenes going on.
One is on Chrome the other on Firefox, so not browser specific
EDIT: Above bug fixed but new one identified.
As you scroll down now the background doesn't scroll, not a major bug but a bug all the same.