unable to login?

whenever i seen lots of people in the xat chat say games back online, i try to click the game, but it keeps saying "Unable to connect to login server. This may be due to a server crash or server check, please check the website as well", i even redownloaded the client and ask the people in xat chat the problem but didnt got an answer, since my friend didnt know the problem even when he was online,and plus i am having a problem getting into the website while other people could.