Hi, some general info about the New Tab page: You can change the number of tiles on the New Tab page by zooming in or out (Ctrl and + key, or Ctrl and - key).

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.

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.' More - Configuration Editor for Firefox.

Note that Firefox should remember the zoom setting on a per site basis.

If the above doesn't answer your question, and especially if the issue started after an update, try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem. Thank you!

You can set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. Adjust its value in 0.1 or 0.05 steps (1.1 or 0.9) until icons or text looks right. Modifying layout.css.devPixelsPerPx affects user interface and web pages (global zoom).

You can open the about:config 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 look at the Default FullZoom Level or NoSquint Plus extension to set a default font size and page zoom on web pages.

• https://addons.mozilla.org/firefox/addon/default-fullzoom-level/
• https://addons.mozilla.org/firefox/addon/nosquint-plus/
• https://addons.mozilla.org/firefox/addon/pagezoom/