User Agent: Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20100101 Firefox/21.0 (Beta/Release) Build ID: 20130511120803 Steps to reproduce: I've installed a fresh installation of firefox 21 on a new Windows 7 computer. Actual results: I don't have any jump lists on the task bar or start menu icons of firefox. Expected results: Jump lists should have existed.

Could you try with a new profile, please. https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

I've created a new profile named test and started firefox with that profile. Nothing has changed in regard to the missing jump list phenomena. I've posted this problem as a question in Firefox Support forum and it seems that this behavior happens to others who've installed fresh copies of firefox. http://forums.mozillazine.org/viewtopic.php?f=38&t=2705519

Interesting. Are you using a special theme on Win 7? In addition, as you're able to reproduce the issue, could you use the tool mozregression (see http://harthur.github.io/mozregression/) to find a possible regression range. FF21 nightlies started in Jan. 2013 (mozregression --good=2013-01-01).

I'm not using any special theme on Win 7 as far as I'm aware of. I'll try to run the mozregression tool to find the regression range and provide results if successful.

Hi, this behaviour has already been noticed, if you would like to comment or follow the discussion, please do it in bug 870529. Thank you for your report!