Firefox trouble displaying text

**dougfir2** · June 9th, 2020

I have an intermittent issue that in Firefox on 18.04 often text is not displayed. I found several references to this and the common guidance was to check your add ons, especially ad blockers.

Example of issue:
Screenshot from 2020-06-09 07-07-52.jpg

Also, over on an online textbook I'm working through here: https://openstax.org/books/algebra-a...ng-polynomials
Screenshot from 2020-06-09 07-01-26.jpg
Note how text are missing with whitespace showing instead.

Here are all my add-ons. I tried switching off every one of them and revisiting the textbook page but the issue persists.
Screenshot from 2020-06-09 07-06-10.jpg

In case it's relevant, I am unsure of which version of Firefox I am on because when I visit software center it doesn't say. Screen:
Screenshot from 2020-06-09 07-16-14.jpg

Does anyone know what my issue is here and how I can fix it?

**Holger_Gehrke** · June 9th, 2020

You can find out the version number of your Firefox by selecting 'Help'->'About Firefox' from the menu.

The screenshot of the forum looks like a font problem, the messed up lines seem to consist of Unicode placeholders (squares with four hexadecimal digits); for some reason ff seems to use a font that does not contain the needed glyphs.

The blank places in the textbook page look like MathML to me when I look at them with the Inspector, on my system they get formatted with the 'DejaVu Math TeX Gyre' font even though there's no reference to that font in the CSS for the page (might be some kind of default for typesetting MathML).

Holger

**Impavidus** · June 9th, 2020

If it's MathML it's probably using a slanted font. The messed-up lines in the screenshot of the forum should also be in slanted font. That could be a lead, but I'm not sure how to proceed from there. You could try reinstalling some fonts...