When browser(Firefox) saves a cached version of website content it reduces any future requests needed for re-downloading code. By default you can only max out to 1GB of saved cache from the web.

Open new tab and type: about:config

• Increase pipelining: search “network.http.pipelining”
  • set network.http.pipelining : true
  • network.http.pipelining.maxrequests: 32
• Increase persistent connections: search “network.http.max-persistent-connections-per-server”
  • set 6 to 8