I woke up this morning to an auto-update message from Firefox saying that beta 5 was available. Aside from some polish and a few bug fixes, beta 5 does have one big change over the last version: by default it will now keep three times as many connections to the server open at once. This change is somewhat controversial so let's look at it in a bit more depth.
Most HTTP servers and browsers use a protocol called "keep-alive" that doesn't close the connection when the client is done with it. This makes sense; opening a remote connection is expensive so it's much faster to open one and download 20 small items than to open and close a connection 20 times. Unfortunately the server can't tell exactly when the client is done, so all these connections are kept alive and consume resources on the server for some time.