Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Check your zoom controls.

<Control> (Mac=<Command>) + (plus) enlarge - (minus) reduce 0 (zero) restore

It is still there when I open Firefox in Safe Mode. When I use the zoom control it fixes it for the one site but not any others. Thank you for helping!

A few thoughts:

(1) If everything is much, much too large, including the toolbars, it could be a problem in the Compatibility settings for your Firefox shortcut.

(2) Firefox has a global zoom factor that affects text size in both the toolbar area AND web pages. We could describe that if you also want to reduce text in Firefox menus, sidebar, etc.

(3) Otherwise, you can use an add-on to set a new default zoom level for web pages. A popular one is: https://addons.mozilla.org/firefox/addon/zoom-page-we/

I haven't used it for a long time, so apologies if its Options layout has changed on the Add-ons page (see the red-boxed setting):

Yes everything is too big including the toolbars and tabs etc. What should I do in that case? Thank you for your help!

Cioccie said

Yes everything is too big including the toolbars and tabs etc. What should I do in that case?

Double-check that your Firefox is not set to run with any compatibility settings. To do that, find the icon you use the start Firefox, and either:

• Right-click a desktop shortcut, then click Properties
• Right-click a Firefox icon pinned to the Taskbar then right-click Mozilla Firefox, then click Properties

You should clear all the boxes on the Compatibility tab for best results (giant screenshot below).

Any difference the next time you start Firefox?

I checked and everything is unchecked. Thank you for your continuing help!

Okay, here's the next thing (#2 on my earlier list):

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste devp and pause while the list is filtered

(3) Double-click the layout.css.devPixelsPerPx preference and enter 1.25 and click OK. This is equivalent to setting the "Text Size" in Windows 7 to 125%.

What do you think, is this the same, better, too large? You can experiment with this setting, but I suggest not making it smaller than 1 and not making it larger than 2 on Windows (or 4 on Mac).

If things get out of control, you can right-click the setting and choose Reset, which is the bottom item on the right-click context menu.

Can you find a size that works well overall?

Is the Firefox user interface affected as well or only the web page area?

Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

Modifying layout.css.devPixelsPerPx affect the entire Firefox window (web page and toolbars).

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

I gave it to our IT dept and they fixed it. I'm sorry I don't know how.