Ok I (tried) to go on the server today, but my Minecraft said: ‘Failed to login: the authentication are currently down for maintenance.’ Please could somebody tell me if it was just my MC or something to do with the server. Also, when I tried to open up MC from the launcher, it said play offline, even though my PC was connected to our wi-fi!? Finally, there were 5 people on PCB at the time according to MC.
Ok I resarted MC 10 mins later and it worked 
Maybe minecraft.net was down.
You could try this link another time
Most of us have had the problem you describe at one time or another - hope this helps you in future.
It was down again when I logged in. Thanks buster for the website, though-it worked very well 