Mozilla Firefox Customer FAQ

The feature you're referring to is called 'Top Sites' and it appears on your Firefox home page. Typically, the sites you visit most often will automatically populate in this section. However, to manually customize this, go to your Firefox homepage and click on the gear icon in the top-right corner to open the 'New Tab Preferences' panel. Here, you can adjust the number of rows for top sites to your liking (up to 4). You may then drag and drop the sites you like to have on your homepage. If you want to pin a site to prevent it from disappearing, hover over the site and click the 'pin' icon that appears.