Why is Firefox so busy?

[kitepilot at kitepilot.com]

OK, I'll confess, I am a WEB site hoarder...
I find sites, open DOZENS of them, leave them open to 
read-them-later/use-them-for-something/show-it-someone-else/forgot-to-close- 
it, you get the drift... 

At any point of time I always have dozens of open pages, just sitting there. 

This morning, they were eating 50% of the power of EACH of my 4 cores...
Which bumped the processor temp to 53 degs C.
Doing nothing...
So I killed the flash plug-in (frequent culprit) to no avail... 

So I bit the bullet and 'kill $(FFOX_PID)' 

All cores happy... 

I restarted Firefox and 'restored it' (which opened up everything I had 
before) and the processor now barely feels the load.  And is at a comfy 37 
deg C. 

Which begs the question:
What in the World was it doing before?
ET