hi
this is from another site.
Invalid HTTP Response:503
It suppose to be an issue from server end. There might be overload on the server/server down at the time of account review.
and
The Web server is effectively 'closed for repair'. It is still functioning minimally because it can at least respond with a 503 status code, but full service is impossible i.e. the Web site is simply unavailable. There are a myriad possible reasons for this, but generally it is because of some human intervention by the operators of the Web server machine. You can usually expect that someone is working on the problem, and normal service will resume as soon as possible.
mcbee