Please read: 1 https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding 2 https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

If this didn't help, please give us more information:

Software: + The Firefox version you're using, active plug-ins and add-ons + Operating system + Do you run other programs while browsing, especially hardware-hungry ones like games, software for editing videos, etc?

Hardware: + Available RAM, available space on your hard drive, processor.

Issue: + When did you first notice that Firefox hangs? + Before that, did you install any new hardware or software or made any other changes to your computer?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

I still having same problem system config. Ram 3 GB Processor-Intel(R) Core(TM)2 Duo CPU E6550 @ 2.33GHz, 2 Core(s),

The Firefox version you're using 39.0 using 2 active plug-ins Operating system win 7 32 bits No other program No games, software for editing videos.

check this:

• see if there are updates for your graphics drive drivers

https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)

https://forums.adobe.com/message/4468493#TemporaryWorkaround

• disable hardware acceleration in the Flash plugin

https://forums.adobe.com/thread/891337 See also:

• http://kb.mozillazine.org/Flash#Troubleshooting