Hi , you can allow websites to choose the own fonts in options this is turned in by default. if it is turned off you can turn it on by opening menu -> Options -> type 'font' in search bar -> under font & colors select Advanced -> Allow pages to choose their own fonts, instead of your selections check the box restart Firefox and reload the website.

Looks you changed from a sans serif font to a serif font. Maybe check the default font settings in "Options/Preferences -> General".

You can also check for font issues in Font Book.

You can right-click and select "Inspect Element" 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