Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All of them.

Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

First I want say very thank you for quickly answer and it work perfect

I really hope This option will be as default in coming Firefox versions

I reply lately as to show if the problem happen again and the problem doesn't happened again

very thanks

I ♥ mozilla Firefox forever

Glad to help.