in my chrome extension I got an div, which I will add to the body of the current tab. I am listening to chrome.tabs.onUpdated. If this event is called, I execute a script inside content_scripts. In this function there I´ll wait till the document is ready with jQuery $(document).ready(...). I try to access $("#div").length and sometimes it returns 1 and sometimes 0. It should added to the body, if it´s not already there. For some strange reasons, the onUpdated event is called twice on each page reload. Actually I found no way to check safely if the div was already added.