Originally Posted by sharphead

Simple really. In the address bar type "about:config" and a list of a whole bunch of options will display. In the area where it says "Filter:" type "network.http" and it'll list only the entries with that word in it.

Now left click and highlight the option:


Right click on the option and click on modify:


Enter in the new value and click OK.


Close browser and restart or continue surfing...