How to prevent browsers from losing connection if idel

Question

Hello,
I'm working on a new windows 2008 R2 server with IIS 7.5 and I'm creating a new website that creates data sets based on user selections.  Currently when I execute a job that is big the browsers time out.  Firefox returns "The Connection has timed out" "The server at ????? is taking too long to respond.  IE and Chrome just continuously spin and nothing is changing on the screen.  Here are the steps I've taken so far. 
1. In Application Pool for my connection I increased Idle time-out to 120 minutes.
2. Within my web.config I added
<sessionState mode="InProc" timeout="120"/>
<httpRuntime targetFramework="4.5" executionTimeout="8192" maxRequestLength="8192" />
How can I make the browsers not lose their connection to the web server?  Some of the jobs could take over 20 minutes.
Thank you