The good news is that Firefox now supports high resolution monitors. The bad news is that this may have the effect of making websites look bigger than you're used to. We'll show you two ways to make Firefox's default zoom level back to the way it was.

Modify the layout

1. Type about:config into the Firefox address bar and tap on the Enter key.
2. If the warning This might void your warranty appears, click I'll be careful, I promise.
3. Search for layout.css.devPixelsPerPx

• Double-click on layout.css.devPixelsPerPx to modify its value. The default is -1.0 in Firefox 22 and above. Change it to 1.0 to make it work like in previous Firefox versions.

If necessary, further adjust in increments of 0.1 or 0.05. Use values between 1.0 and about 0.5 to reduce elements in size. Use values greater than 1.0 to increase size. For example, a value of 1.25 will increase font size to 125% to accommodate the default DPI setting in Windows 8. Double check the value that you enter. Setting a too small value will make everything disappear and a too large value will make things too wide.

Install NoSquint and set the global page zoom to 80%

This should restore the previous page zoom behavior.

1. Open the NoSquint page on the Add-ons website.
2. Click the green Add to Firefox button to install NoSquint.
3. When the installation is done, you will be prompted to click Restart Now to complete the process.
4. When Firefox restarts you will see a magnifying glass in the Add-ons bar at the bottom of the Firefox window. Click the magnifying glass to open the NoSquint settings.
   
5. In the NoSquit settings window, click Global Settings. This will open an additional Global Settings window.
   
6. In the Global Settings window, click on the Zooming tab and change the Default full page zoom level to 80%.
   
   Note: This is based on Windows setting the computer default to 125%. If this is not the case on your computer, you might have to experiment with something different than 80% to get the results you want.
7. Click OK to make the change and close the Global Settings window.
8. Click OK to close the NoSquint settings window. The process should now be complete.

You may notice that NoSquint adds a + and - button to your toolbar. If you want to remove them you can click Remove toolbar buttons on the NoSquint page that opened when Firefox restarted. If you don't have that page open any longer you can always remove them with these instructions.