Open a new tab and click on the Cog icon to display the New Tab Controls. You can choose between Show your top sites and Show blank page:
Show Your Top Sites
Firefox will display the websites you visit the most in the New Tab Page. You can rearrange tabs around or pin your favorite websites to the New Tab Page for easier access.
Furthermore, you can get relevant suggestions and discover new websites by ticking the Include suggested sites checkbox.
You can change the maximum number of websites displayed in New Tab Page by editing the browser.newtabpage.rows (max number of tiles per row) and browser.newtabpage.columns (max number of tiles per column) attributes in your Firefox preferences (about:config window).
Show Blank Page
Choosing the Show Blank Page option will simply display a new blank page upon opening a new tab.
Alternatively, if you'd like to open new tabs to a specific URL (i.e. Google.com), you can learn how to enable these page settings in our article entitled Open New Tabs with a Specific URL.
Customize Firefox's Default Tab Settings
Click on the Menu button > Options:
Go to General > Tabs . Here, you'll find all the options related to tab management in Firefox:
Enabling the Open new windows in a new tab instead option will open any ads, pop-ups, or links in a new tab instead of a new browser window.
The Don't load tabs until selected option will stop a page from loading until a user clicks on that specific tab. For more information regarding this option, please read our tip Don't Load Tabs Until Selected.
When enabled, the When I open a link in a new tab, switch to it immediately option will bring any new tabs to the front of your screen automatically (set the new tab as the active tab).
Finally, activating the Show tab previews in the Windows taskbar option will display the thumbnails of your opened tabs when you hover your mouse cursor over the Firefox icon (taskbar).