Firefox automatically adjusts the number of columns that fit on the about:newtab page if you adjust the width of the Firefox window or zoom the page in or out and no longer resizes the thumbnails. Current releases do not resize thumbnails, but instead reduces the number of tiles to fit the screen width, so you may not see the number of columns that is specified via the browser.newtabpage.columns pref. Zoom out the about:newtab page to see more tiles. Make sure that you have only one tab with the about:newtab page open. You can toggle browser.newtab.preload to false on the <b>about:config</b> page if you do not keep the zoom setting. You can open the <b>about:config</b> page via the location/address bar. You can accept the warning and click "I'll be careful" to continue. *http://kb.mozillazine.org/about:config You can also look at this extension: *New Tab Tools: https://addons.mozilla.org/firefox/addon/new-tab-tools/