It's not. Same thing was happening last year. It's just a bug somewhere in the website that shows up sporadically. (I'm thinking that somewhere along the line, between browser settings, cache stuff, and whatnot, the button's link becomes all wonky (yes, that's a technical term!) and points to the wrong file. A file that should be part of the final rendered page).
Try clearing your cache/cookies and/or using a different browser to see if that has any effect.
This knowledge base article from Indiana University should explain the procedure on most of the common browsers (except Chrome).