Unread Tabs Restorer for the win. Works in firefox nightly now.
install extension
add this code to your userchrome.css
look up how to do that easy but need put in your profile folder and change preferences in about:config -->turn on toolkit.legacyUserProfileCustomizations.stylesheet
add this code to userchrome file .tabbrowser-tab[pending] { /* Set styles for unloaded tab */ } .tabbrowser-tab[busy] { /* Set styles for loading tab */ } .tabbrowser-tab[unread] { /* Set styles for unread tab */ }