Is this with many websites, some, a few?

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}

If there is still a problem, Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Did this help?

While you are in safe mode;

Try disabling graphics hardware acceleration in Firefox. Since this feature was added to Firefox it has gradually improved but there are still a few glitches.

How to disable Hardware Acceleration {web link}

Thank you for your speedy reply ...

This problem is occuring on only the one sites at present ...https://www.nrl.com/. This site works fine in Safari and Chrome

I have actioned all of your recommendations and the problem still exists ?

Regards Adrian

Special icons are usually supplied by an icon font that is downloaded from the server (@font-face) You may see little boxes with the hex code of the character if you do not have a font installed that covers this Unicode range.

You can check gfx.downloadable_fonts.enabled on the about:config page and make sure it is set to true (if necessary double-click the line to toggle its value to true).

The website uses this special font for the videoplayer:

@font-face {
  font-family: videoplayer;
  src: url("public/d14810f2fa89c51ca63f74ac26bdf92b.woff2") format("woff2"), url("public/1447d74dea469a11f47d9fa37e339312.woff") format("woff");
  font-style: normal;
  font-weight: 400;
}

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows the shield icon at the left end of the location/address bar in case Content Blocking is blocking content.

• click the shield icon for more detail and possibly disable the protection

You can check the Web Console about what content is blocked

• "3-bar" menu button or Tools -> Web Developer
• https://support.mozilla.org/en-US/kb/tracking-protection
• https://support.mozilla.org/en-US/kb/content-blocking