Hello For information purposes. Maybe, perform tests, with, userContent.css file, take a look at pages below. https://connect.mozilla.org/t5/discussions/feedback-for-the-new-tab-layout-variants-in-the-home-page/m-p/101511/highlight/true#M39447 Or, this, userContent.css file. https://connect.mozilla.org/t5/discussions/feedback-for-the-new-tab-layout-variants-in-the-home-page/m-p/101736/highlight/true#M39514 Other subject ? https://bugzilla.mozilla.org/show_bug.cgi?id=1979767