Hi, it is very frustrating when I use tab groups in iceweasel, because it is so sloooow. The problem seems to be xorg which loads the cpu to 100% when displaying and managing tab groups. I have the same problem on occasional web pages.
My system: - cpu: Intel Core2 Duo 64 bit; - debian amd64, stable and testing; - iceweasel 16.0.2 (but I had the problem also with version 10.x and previous); - video card nNVIDIA quadro135M and nvidia driver (nvidia-kernel-legacy-173xx-2.6.32-3-amd64). Thanks for any help, Davide