have not got a clue
I don't know either but I do know what problems it causes.
Firefox not responding.
Firefox using too much memory process.
Afeter going through a few things in FF help I ended up have to do a roll back on my pc cos it messed the graphics up
I have to use Chrome for gaming as FF is a waste of time.
Some info here about updating the graphics display driver.
For freezing problems try this:
The default of the pref network.http.max-connections has been increased from 30 to 256 in Firefox 6+ versions.
You can try to decrease the value of the pref network.http.max-connections from 255 to a more modest setting like 30 as used in Firefox 3 versions.