Type: about:config in the address bar, Then look for the following entries, and make the corresponding changes.

1.network.http.max-connections-per-server =32
2.network.http.max-persistent-connections-per-proxy =16
3.network.http.max-connections = 64
4.network.http.max-persistent-connections-per-server = 10
5.network.http.pipelining = true
6.network.http.pipelining.maxrequests = 200
7. network.http.request.max-start-delay = 0
8.network.http.proxy.pipelining = true
9.network.http.proxy.version = 1.0

AND YOUR ALL DONE!!!