You can check for issues with (corrupted) fonts. You can right-click and select "Inspect" to open the built-in Inspector with this element selected. *https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/open_the_inspector/ *https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/examine_and_edit_html/ You can check in the <b>Rules</b> tab in the right panel in the Inspector what font-family is used for selected text. You can check in the <b>Fonts</b> 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. If the Fonts tab is hidden, click the down arrow at the right end. *https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/edit_fonts/ You can try to disable hardware acceleration in Firefox. *Settings -> General -> Performance<br>remove checkmark: [ ] "Use recommended performance settings"<br>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 apply changes. *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