ASP page post and Web Server

I have Page1.asp which is posted to Page2.asp.
Page2.asp runs in hidden frame. When web server is running and Page2.asp is
running I can pass suceess / fail / any error messages to Page1.asp using
javascript.

Now if Web server is down then Pag1.asp progress bar is running continuously
and have no idea whats going on whethere there is logic error or error due
to web server down.

How to handle this smartly and propogate an error to page1.asp