To access the internet through firefox, you need to set the proxy server. Open firefox, go to "Edit --> Preferences --> Network --> Settings" and tick "Manual Proxy Configuration". Enter the information "proxy.iisc.ernet.in" for the proxy, and "3128" for the port. Tick "Use this proxy server for all protocols", and enter "localhost, 127.0.0.1, .iisc.ernet.in" in the field that says "No proxy for". Now you should be ready to surf the web.
When you want to surf the web outside IISc, the proxy server asks for a login and a password. You have to get these from SERC by registering as an official IISc person. If you have not registered, then you can access the web using "noauthproxy.iisc.ernet.in" (all the other fields remain the same) which is slower.