Maximize connections to multiple servers
The integer preference network.http.max-connections controls how many simultaneous network connections Firefox will make at any one time to any number of Web servers. One typical way this pays off is if you have Firefox set to load multiple home pages in different tabs at once, or if you access pages that aggregate contents from several different servers (for instance, multiple advertising systems).
By default, this is set to 24, which should work well for most network connections, but you can raise it to 32 and see if that has any effect. (I've seen people raise this as high as 64, but anything above 32 doesn't seem to provide much discernible payoff.)
Maximize connections to the same server
The integer preference network.http.max-connections-per-server controls how many separate connections Firefox makes to the same server, which allows multiple elements in a page to be downloaded in parallel. Normally, this is set to 8, but some people choose to set it as high as 16.
Note, however, that some Web servers will block you if you try to establish more than 8 inbound connections, typically as a bandwidth-protection or antileeching measure -- this is the kind of behavior also exhibited by download managers that try to use as many "slots" as possible to speed things up, and many server admins hate that sort of thing. Also, if you're on a connection that's not fast to begin with (e.g., slow ISDN or dial-up), changing this setting will have no discernible effect, and may in fact slow things down.
