From MozillaZine Knowledge Base
HTTP is the application-layer protocol that most web pages are transferred with. In HTTP 1.1, multiple requests can be sent before any responses are received. This is known as pipelining. This preference specifies the maximum number of requests to pipeline at once when pipelining is enabled.
Possible values and their effects
Any integer from 1 to 8 inclusive determines the maximum number of requests to pipeline at once. A value of 1 disables pipelining. (Default: 4)
Higher values will cause a delay before the first request completes but will make the last request complete sooner. Higher values will also cause more of a delay if a connection fails.
First checked in
Has an effect in