Just saw this and tried it out and it works pretty damn good.
These tweaks will speed up Firefox so pages and videos will load alot faster.

Step 1: Go into your address bar and type without quotes "about:config"
Step 2: In the filter box type "network"
Step 3: Scroll down till you find "network.http.pipelining" double click it to change it to true.
Step 4: Under that look for "network.http.pipelining.maxrequests" and set that somewhere between 50-100. if you notice lag set it lower.
Step 5: Restart Firefox and enjoy.

Thanks :)