Firefox: Remove Mozilla Announcements / Video window on Startup page. From time to time Mozilla places announcements and a video window on the Firefox Startup page. Here is how to prevent those announcements and video window from appearing. In Linux or Windows 10, Firefox: In the Firefox URL field type: about:config and press ENTER. Click the "I'll be careful, I promise!" button. In the search field type: snippets locate the following string: browser.aboutHomeSnippets.updateUrl double-click on above string. clear the URL in the "Enter string value" popup window. click OK ----- On the Firefox Menu Bar click: Help, Troubleshooting Information, On the page that opens scroll down to: Application Basics, Profile Folder, click "Show Folder" button. A window showing Firefox folders will appear. click on /storage folder click on /permanent folder Leave this folder window open. ----- Using the Firefox Hamburger Menu icon in Firefox (the 3-Line Icon on upper right) "EXIT Firefox" using the circle-with-a-line-through-the-top icon on bottom-right of popup menu. ----- Go back to the open folders window. now delete the /moz-safe-about+home folder Close folder window. ----- Now restart Firefox and the Mozilla announcements / Video window should be gone from the Firefox Startup page.