The elements that you are having issues with are actually not images, they are custom fonts. In the past, websites used to make icons using image files, but now it's common practice to use a custom font file or a font pack online (like Font Awesome, for example).

In the Fonts & Colors section of Firefox, click the Advanced... button and ensure that that Allow pages to choose their own fonts, instead of your selections above box is checked. Otherwise, websites will not be able to load the custom font files that they use for icons and you may get issues like you are currently having.

Hope this helps.

Thanks, Wesley. Your reply not just helps. It solves the problem. I appreciate your input.

Perhaps Firefox should disable this setting/option, as it breaks pages and people like me don't know what causes it.

Glad I could help!

Perhaps Firefox should disable this setting/option, as it breaks pages and people like me don't know what causes it.

It has some practical use-cases, but for most users it should always remain enabled, as it normally is by default. However, as you've already alluded to, it's commonly the cause of many issues.

See also:

• Bug 789788 - Not allowing pages to choose their own fonts breaks with icon fonts

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)