Reader Don MacKenzie would like a more efficient way to download files from his favorite websites. He writes:
I visited a website that had links to a lot of MPEG-4 movies that I wanted to download. I use Firefox and when I clicked on each download link I found that Firefox would only download two movies simultaneously. I had to wait until one of the movies was completely downloaded before I could download the next. I thought Firefox supported simultaneous downloads. Is it really limited to just two downloads?
By default, yes. But you can change it by typing about:config into the address field, typing persistent into the Filter field, and double-clicking on the network.http.max-persistent-connections-per-server entry. In the sheet that appears, type in a number larger than 2 (this will be the number of simultaneous connections Firefox will support). Quit Firefox and relaunch.
Once you do this you can download more files simultaneously. You’ll find it easier to do so with the help of the DownThemAll extension.

DownThemAll allows you to download all the linked files on a page or just a selection of particular file types. For example, you can ask it to download just a page’s video files. This queues the downloads so you don’t have to hang around clicking download link after download link.
Updated to correct the notion that a site’s server determined the number of files you could download simultaneously. Hat tip to forum visitor mac_savant.