This shouldn't be surprising as most websites don't support really old browsers. Mozilla/5.0 was released 11 years ago. Security issues in that browser version alone would be reason enough to outright block access from it.
Note, Microsoft has been moving away from MSDN forums for a while now to Microsoft Q&A. I used to be an admin for a half dozen MSDN forums and we moved all those to Microsoft Q&A over 2 years ago.