So I think most of us set the value to 100(http://www.ocforums.com/showthread.p...hlight=FireFox), and some went further...but apparently the max is 8.

network.http.pipelining.maxrequests


* Description: maximum number of consecutive requests in one pipeline.
* Type: integer
* Limit: 8
* Default: 4
* Additional Info: nsHTTP.h. Optimal value depends on connection bandwidth/latency.
* Recommendation: 8. While it doesn't hurt to set it to 100 like in other tweak examples, it will have no effect whatsoever because of the mentioned limit.

http://forums.mozillazine.org/viewtopic.php?t=53650