My Aspx Page call Twice
You could experienced the same like me. It is because you set the aspimage or just <img src="" runat="server">
So if you set the image source to nothing Fire fox will append to attribute and set the src to your aspx page ex:http/localhost/mysite/mypage.aspx.
and it will try to get the image request to your aspx page.
If you see the second request header is asking for Image type
so the solution is add a dummy url if it's empty