I've noticed the JavaScript takes a lot of CPU on Iceweasel/Firefox, but Chromium scales down the refresh rate instead.
It's mainly due to the 1 sec refresh on 250 transactions,
leads to memory issues sometimes if left on for a long
period on Firefox, I have noticed. Chrome is fine however.
Refresh usually sorts this out, the aim wasn't for the site
to be left open 24/7 so I don't really plan on changing it
although I am aware from monitoring that lots of people
leave the site open for 24 hours+ a time, i'll see if I can
create a more efficient refreshing system when I have
the spare time.