First, a bit of business: you may not have read our naming policy on the way in. It requires that you use a full, real (sounding) first and last name for your display name. Nicknames or "handles" aren't OK here. You can change your display name here. Thanks!
That's a server error message, and means that the server refused to honor the request. You might want to look at the server logs to see which file was specifically requested, whether that's in fact the file that should be accessed, and if there are possibly more error messages in the server log.
subject: Loading problem of signed applet on MAC OS