Do you have
www.minecraft.net/play bookmarked? If so, it has updated since then, and it is now
www.minecraft.net/classic/play. Not totally sure if it'll work or not D: If that doesn't work, try reinstalling java. If that doesn't work, try deleting your temporary internet files.
1) Close browser
2) Goto: Control panel > Java > General > Temporary Internet Files > Settings > Delete files
3) Open browser and try again