Follow This Steps :
1. Type " about:config " on address bar
2. In Filter, Find " network.http.pipelining " Doulble click and change value to " True "
3. Then Find " network.http.pipelining.maxrequests " and set value to "8"
4. Find "network.http.proxy.pipelining" and set to "True"
5. Find "network.dns.disableIPv6" and set to "True"
