'''How do I change the icon for an app-tab?...'' You can restore the dog-eared white sheet for pages without favicons with a style. I guess what was really annoying is that the dotted outline makes it match the background besides being an unnecessary change. First install the Stylish extension to manage styles. * [https://addons.mozilla.org/firefox/addon/stylish/ Stylish :: Add-ons for Firefox] (248.8 KB) * [http://userstyles.org/styles/56126/fx-8-restore-default-favicon-on-new-blank-tabs Fx 8 - Restore default favicon on New/Blank Tabs - Themes and Skins for Browser - userstyles.org] Since you are using the app-tabs in rather constant positions you should be able to recognize each tab by its relationship to those around it by the patterns of favicons and those without them. I have 3 .txt icons 6 with Firefox as here in support (4 of them are together) and 7 with distinctive icons. You can reorder the tabs by dragging them to a new position within the app-tabs area. For those that want to assign a favicon to a bookmark that doesn't have one or to chane it, there is * Favicon Picker 2 :: Add-ons for Firefox (57.3 KB)<br>https://addons.mozilla.org/en-US/firefox/addon/favicon-picker-2/ To change the favicon the webpage must be bookmarked, but you really want to bookmark those you use as app-tabs as a group into a bookmark folder so that you can restore them as a group when you you mess them up, or accidentally delete a few or all of them.

Thanks very much, dmcritchie. I'll try that later on and let you know if it worked for me... or if I have questions about what you wrote.