There has been a sporadic problem lately with the OGame login page. Judging from the forum posts on the subject, this is due to DDOS attacks. Whatever the cause, though, people are looped back to the login page when they attempt to login.
The only way to bypass this has been to use a different login page, such as ogame.co.uk. These pages can have the same issues, though. There are emergency login pages which always work, but they don't usually have the newest universes.
The best solution to this is to create and use your own login page. To do so, copy the text here into a notepad document, save it as "OGame Login.html", and open it in your browser.
To update it with new universes, find the previous universe's entries and add ones for the new universe immediately after them. There are two entries per universe, one for login and one for registration.
While this page will allow you to get to the registration page for universes that aren't accepting registration, you still won't be able to register.
Ideally, you could edit the page to include only universes you play in, and autofill your username and password. Or you could even set it up as a bookmark which would automatically log you into a single account.