Is this with all websites/pages, some, a few?

Type about:preferences#general<enter> in the address bar. Across from fonts and colors, press the Advanced button. On the bottom, turn on Allow Web Sites To Choose Their Own.

Make sure you haven't enabled a High Contrast theme in the OS settings.

Also see: https://support.mozilla.org/en-US/search/advanced?q=fonts&language=en-US&product=firefox&sortby_documents=relevance&a=1&w=1

Those settings were alredy OK. So this did not solve my problem

Do you get same errors with Chrome and MSEdge?

No when I use chrome everything is OK. But I sometimes have the same problems with google translate

I have this problem especially with LingQ a language website. I have discussed it with them but they did not regognize the problem at their side. So I swithed to the Chrome browser.

So LingQ has not tested their website with FireFox ?

So you say this occurs with Google Tanslate too?

What is the language that is not showing up clear?

Can you copy and paste the paragraph here for us, that is creating the errors; as i dont speak the LingQ but can try to replicate the error on my end.

The language does not make any difference you can change this language in the settings. From the screenshots I have sent earlier yuo can see the missing letters are also in the left column. If you change the size of the window than especially this fenomena appears.

Her is a screenshot of gmail from google

Looks like a font problem.

You can right-click and select "Inspect" to open the builtin Inspector with this element selected.

• https://developer.mozilla.org/en-US/docs/Tools/Page_Inspector/How_to/Examine_and_edit_HTML

You can check in the Rules tab in the right panel in the Inspector what font-family is used for selected text. You can check in the Font tab in the right panel in the Inspector what font is actually used because Firefox might be using a different font than specified by the website.

• https://developer.mozilla.org/en-US/docs/Tools/Page_Inspector/How_to/Edit_fonts

I do not develop websites. I just use websites with the help of your browser. This answer does not help me at all.

thanks for the screen shot. and i am not happy with what you are getting.

let me / us ponder about this, see all the steps taken and figure out a solution for you.

i would like to reproduce the issue though

btw what is the other language involved?

is it greek, maybe?

You can try to disable hardware acceleration in Firefox.

• Options/Preferences -> General: Performance
  remove checkmark: [ ] "Use recommended performance settings"
  remove checkmark: [ ] "Use hardware acceleration when available"
• https://support.mozilla.org/en-US/kb/performance-settings

Close and restart Firefox after modifying the setting to make changes effective.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

Thanks for your help. I removed the hardware acceleration check mark and this has solved the problem so far as I tested it.