It's a mac mini 1.42 GHz G4 (7450) with the max ram of 1GB DDR SDRAM.
I figured out the glitch with the typing I have to set the cursor in the box and wait a few seconds for things to load I traced it back to a plugin called FBP "Facebook Purity" it changes the code around to get rid of annoyances but call times are longer on this old box. With that plugin disabled page load times are faster and the glitch dose not happen so I will have to live with this if I want to continue using it. Also dose prefetching and network.http.pipelineing increase memory usage when enabled in about:config? got both set low maxrequests and max-optimistic-requests set to 2. Seems to make pages load faster when these are enabled.
I would strongly recommend against prefetching. What
happens in that case is that the browser will try to guess where
you'll go next and have those resources ready. On a multiple CPU
machine this might pay off if it guesses right (it doesn't always),
but on a single CPU like your mini you will spend additional time
grabbing those files and trying to handle them at the same
time the browser is trying to handle the page you're currently
looking at. It will certainly increase memory usage trying to get
those files speculatively, and it will probably make things slower
As far as pipelining, you can try it and for many sites it does
improve things, but for other sites it's a wash and a few sites
will not work properly, which is why it is not the default.