This is happening to everyone right now for reasons unknown, though my best guess would be that they're finally migrating the authentication to its own server, which handles minecraft.net connections from clients and, presumably, from browsers as well. We can't do anything about it except wait.
Rollback Post to RevisionRollBack
"Call me Endy. If you have trouble with Minecraft, I'll be more than willing to help."
Hi everyone just giving an update on the screw up of the game.
Me and Tobias Mollstram, who is the head of the minecraft tech stuff at mojang. Have been tweeting each other, I asked him "What is wrong with the game, is it currently having something to do with the server update, authentication server change around, etc" note that i did put a few '.....Contuines" in teh tweet, He replied back "Yes we are currently moving authentication servers and that to a new (cant remember what it's called). The game will be down for a while, so just hang on a while". A few '.... Contuines' aswell.
So they must be doing a major fix on the game and that. We just gotta wait.