By default, there are 8 tiles for the important pages on the New Tab page in Firefox , centered and next to each other, each in a row. If you would like these tiles to be larger and across the entire width of the page, you can do this with a CSS code.
This is what it looks like by default:

Firefox – New tab page the tiles bigger
Create userChrome.css and userContent.css
reuse userChrome files
And this is how it is done with the CSS code.
First, we go to the Firefox profile folder and open the chrome folder that we created there.
Then open the userContent.css file in the chrome folder.
We now enter the following CSS code in this file:
/* new tab tiles to full page width */ @-moz-document url(about:newtab), url(about:home) { main { width: 100% !important; } li.top-site-outer { padding: 5px 40px !important; } div.tile, div.tile div.screenshot { width: 150px !important; height: 120px !important; } .top-site-outer .title.pinned span { width: 150px !important; } }
Firefox – New tab page the tiles bigger
And this is what the code looks like in the userContent.css file:

And this is what the New Tab page looks like after the change:

Since the tiles are now wider, fewer fit (6 instead of
side by side.