"Accept" is a valid Request Header Field. This means it is valid in the context of a client requesting a resource to the server.
In this case, however, it was send the other way: from the server to the client. Probably just an error from the programmer who didn't read the RFC with enough care.
This header is not used by any known client.
HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
Content-Length: 2133
Accept: */*
Date: Fri, 30 Jul 2010 17:04:02 +0000
<!DOCTYPE html PUBLIC "-//W3C//DTD ...
...
...