I've checked the info and all looks correct assuming you are using the profile name called: hp45ddwp.default-release. 'chrome' folder is spelt correctly and it is in the profile name folder 'userChrome.css' is spelt correctly and it's Type is css document and it is in the 'chrome' folder. The code in the 'userChrome.css' file appears correct. I've just modified the code by adding some text above the code part. So take another look at the full instructions I posted in an earlier comment. It might make a difference, so try it. I did try without it and with it and it made no difference. Remember you must fully exit Thunderbird before editing the 'userChrome.css' file. but usually if you have chrome folder in the profile name folder (which you are using) and it contains a 'userChrome.css' file with code - then I'm thinking the legacy option in config editor is still set on false. Just so we are clear on this - the code removes the address book icon from the Spaces Toolbar. I removed the 'Chat' icon as I do not use it.