Please check if Firefox is running in Windows Compatibility mode - see here.

Otherwise, check any extensions you might be running - see here.

If still no luck, please have a read through the article Firefox consumes a lot of CPU resources for other possibly causes.

Don't hesitate to contact Firefox Help again if you are still having trouble.

I unistalled some disabled/not compatible add-ons which where used at older firefox versions and after a couple of firefox and windows restarts i see a really big progress. plugin-container.exe mostly uses 0% of cpu load! So, the problem solved for now but with not a really satisfying way. I mean that the problem still exists but whithout those add-ons it's like sleeping!

However, I really really thank you for your help and interesting.

disable unneeded plugins....

nvidia 3d vision isnt necessary if you dont have a 3d compatible screen. google update is unneccessary too....

the problem re-appeared... i tried the above solutions of shusseina but nothing changed. ammar.sakarwala, thank you, i will try your suggestion too.

ammar.sakarwala, i have also disabled the unnecessary plug-ins like the one you told, but even now nothing happened! i think that a problem like can be solved only from Mozilla's developers!

well... then the only thing left is a clean reinstall....

den install back only the necessary and compatible addons...and then disable unnecessary plugins.....