Is that the only page where you see a broken display like that?

Only some of the style rules are not working in your screen shot, so I can't figure out how the page got that way.

Have you already tried these things:

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes.

(2) Remove cookies for gmail.com (should not affect google.com). While viewing a page on the site, try either:

• right-click the page and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the padlock or globe icon in the address bar > More Information > "View Cookies"

In the dialog that opens, gmail.com should be filled in at the top, so you can remove the site's cookies individually.

Then try reloading the page. Does that help?

Could you test in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

You can check the Net log and the Network log in the Web Console (Firefox/Tools > Web Developer) to see if content fails to load or possibly is blocked (file size is zero).

• https://developer.mozilla.org/Tools/Network_Monitor
• https://developer.mozilla.org/Tools/Web_Console

Use Ctrl+F5 or Ctrl+Shift+R to reload the page and bypass the cache to generate a fresh log.