Due to a confessed vulnerability in Flash version 18.0.0.203, Mozilla soft-blocked that version of the plugin. Therefore, you needed to activate it on sites you trust to use it instead of being able to set Firefox to let all sites use Flash automatically. I'm using the past tense because Adobe released an update today. You can get version 18.0.0.209 on this page: https://www.adobe.com/products/flashplayer/distribution3.html In the first table, look for the row for "plugin-based browsers" and you can use either the EXE or the MSI installer. Then things should be back to normal. ---- No one can promise that this kind of block will never happen again. Should that occur, if you are not accustomed to using the "Ask to Activate" feature for a plugin, here's what to expect: When you visit a site that wants to use Flash, you should see a notification icon in the address bar and one of the following: a link in a black rectangle in the page or an infobar sliding down between the toolbar area and the page. If you see a good reason to use Flash, and the site looks trustworthy, you can go ahead and click the Lego-like icon in the address bar to allow Flash. You can trust the site for the time being or permanently. But some pages use Flash only for tracking or playing ads, so if you don't see an immediate need for Flash, feel free to ignore the notification! It will just sit there in case you want it later.