What event fires to an firefox extension when the back button is selected or history item is selected

My extension needs to know that the tab is displaying something from the history rather than the latest loaded document.

onload doe开发者_开发知识库sn't seem to be the right event. It doesn't always fire.

Use the pageshow event, it fires after the onload event and has a parameter called persisted that will be set to true when the page is loaded from the cache.