I will just repeat this it should help: (Please post back to say if it helped or if you need other assistance ? ) ''Firefox 39 Tile Problems?'' [/questions/1070115] '''''Scribe''' [/questions/1070115#answer-748711 said]'' <blockquote> Hi, you can change the number of tiles on the New Tab Page by zooming in or out (Cmd and + key, or Cmd and - key). <br /> <br /> You may also want to keep the same zoom setting when clicking on a new tab: Type '''about:config''' into the address bar, press Enter, accept the warning, scroll down to '''browser.newtab.preload''' and double click on it to change 'Value' from True to False. <br /> <br /> It is also possible in about:config to change the maximum number of tiles, by scrolling down to '''browser.newtabpage.columns''' (or '''.rows'''), then right click > Modify, to set a new number in 'Value.' <br /> <br /> As an alternative, you may like to try the add-on [https://addons.mozilla.org/en-US/firefox/addon/new-tab-tools/?src=search New Tab Tools.] <br /> <br /> ''If your question is resolved by this or another answer, please take a minute to let us know. Thank you.'' </blockquote>

This doesn't work if you have "Zoom only Text" on, just FYI.