Is this problem on... * Your Windows 7 system * A FirefoxOS device * Firefox for Android (You posted using a browser that said it's running on Windows 7, but your question ended up under FirefoxOS, which is a phone operating system.) ---- As for what the missing plugin is, usually it is a media player of some kind. Do you want to post a link to the page, assuming no login is needed? The following page is designed to list out your usable plugins. It has a box you can click/tap to copy/paste into a reply: https://jeffersonscher.com/res/plugins.html