ASPX WILL NOT OPEN I

Hi,

I am working on a web site in ASP.NET, I have been testing it win IE7 all works fine. I installed Firefox and Netscape. When trying to open the main Index Page I keep getting a windows that is indicating:

You have chosen to open
which is a : application/octet-stream

what should Firefox do with this file?

It opens without any problems in IE7 I’m I missing something?