HTTP is the application-layer protocol that most web pages are transferred with. The total number of HTTP connections the application can make is limited by this preference. If more connections are needed, they are queued until a connection "slot" is available.
Possible values and their effects
This integer preference takes values between 1 and 65535 inclusive, directly corresponding to the maximum number of HTTP connections Mozilla can have open at once. The default value is 24 for all applications except Minimo, whose default is 2.
- In Firefox 3, the default has been raised to 30.
- In Firefox 6 desktop, the default has been raised to 256.
- In Firefox 8 desktop on Windows, the default has been reduced to 48. 
- The Windows default was set back to 256 after the bug was fixed (probably in Firefox 10).
Users on slower connections may want to reduce this number to help prevent HTTP connection timeouts. Users on faster connections may want to increase it, but the default value is usually fine for normal usage.
First checked in
Has an effect in
- Netscape (all versions since 6 Preview Release 1)
- Mozilla Suite (all versions since Milestone 15)
- Mozilla Phoenix (all versions)
- Mozilla Firebird (all versions)
- Mozilla Firefox (all versions)
- SeaMonkey (all versions)
- Camino (all versions)
- Minimo (all versions)
- Bug 33259 - So, should we make a number of http connections configurable
- Bug 423377 - Change max-persistent-connections-per-server to 6.
- Bug 648570 - increase total idle pconn tool to 256 (matches chrome)
- Bug 692260 - Increase in network.http.max-connections appears to cause hang, requires browser restart
- Bug 696989 - Lower network.http.max-connections to 48 on windows until bug 692260 is resolved