From MozillaZine Knowledge Base
HTTP is the application-layer protocol that most web pages are transferred with. This preference controls which version of HTTP to use if a proxy server is configured.
Possible values and their effects
Use HTTP 1.0.
Use HTTP 1.1. (Default)
This preference should usually be left at the default of 1.1. Some proxy servers require that 1.0 be used.
First checked in
Has an effect in