What Fluorita says is right. I had a similar case during last month's patch, where I refreshed the page, got the server list, figured the patch was over and game was up, so got in and tried to get a head-start on the events before the crowds came. Only later did I find out this was unintentional and I and others weren't meant to be in the game.
Since then I've avoided trying to login until there's an official go-ahead from Mazinger or whoever, but it wouldn't surprise me if other people continue making this mistake, especially new players too ignorant to know something was wrong (such as was my case).
I don't know why the server list sometimes appears when the page is refreshed, but preventing that from happening, if possible, should stop people from being able to log into the server prematurely.