That's an indication of a font issue.
Launch the FontBook app located in your Applications folder.
From the Font Book menu bar click Font Book > Preferences then select: Resolve duplicates by moving files to the Trash
Quit then relaunch Safari to test.
If that didn't help, with the Font Book app open, back to the menu bar click File > Restore Standards Fonts
Be aware, third party fonts will be placed in a, "Fonts Removed" folder next to the Fonts folder.
Quit then relaunch Safari again.
If that didn't help, booting in Safe Mode deletes font caches.
Top left corner of your screen click the Apple > Shut Down.
After your Mac shuts down, wait 10 seconds, then press the power button.
Immediately after you hear the startup tone, hold down the Shift key. You should press the Shift key as soon as possible after you hear the startup tone, but not before.
Release the Shift key when you see the gray Apple logo and progress indicator.
Once you are in Safe Mode, go back to the Apple menu. From the drop down menu click: Restart
Then try Safari.
About Safe Mode
* message edited by; CS