This has been the case since a very very long time, with no issue in IE. Currently on FF 38.0.5, and did some searches and found this https://support.mozilla.org/en-US/questions/1012607 which suggests the icons are really a font [this method is used by Excel too]. In this case, the icons font is suggested to come from @font-face??.

Followed the instructions, found the config was in fact set to true but toggled anyway, restarted firefox, but no change. Restarted FF clean without any add-ins **, still no change. Question is, what is blocking the icons to show in FF and mostly makes the statistics part of the website dis-functional?

TIA

** Instructions here: https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Forgot, on my Stats page in FF also cannot see the charts, which too are visible in IE.