User Agent: Mozilla/5.0 (Windows NT 6.0; rv:39.0) Gecko/20100101 Firefox/39.0 Build ID: 20150630154324 Steps to reproduce: I switch on the function "DIV-Abmessungen anzeigen" (Web Developer-Tools) Actual results: It works, but when I open another tab and browse to the webpage i.e. Ebay, it will occur on each website.And further, it will not distinguish, even when I remove the check mark at "Div-Abmessungen anzeigen". When I click on the check mark again, the function will distinguish, but the check mark is still there ! Si,the sense of the check mark changed to 180° . Expected results: The function"DIV-Abmessungen anzeigen" should regard just one tab and it should be removable at once !