Make sure that you allow pages to choose their own fonts.

• Tools > Options > Content : Fonts & Colors > Advanced: [X] "Allow pages to choose their own fonts, instead of my selections above"

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

This may not be an issue with Firefox. There are a number of reasons that this could be happening. Here are a few ideas to get you started:

1. Where is this webpage hosted? Is this on a server somewhere? Or is this a local page?
2. If on a server, are all of the paths correct in the code? (CSS and links to font files?
3. If hosted locally, do you have ALL of the needed files on your computer? (CSS, Fonts, etc.) And are the paths correct?

Outside of those issues, I can't think of anything else that would be causing this without looking through some HTML/CSS.

@cor-el : I done all that but still have the problem, i also reset Firefox but still have the problem

@seancannon i test it local and online its OK on my friends Firefox and it just my problem.

its a test page for example that i have the problem with https://dl.dropboxusercontent.com/u/28793409/fontello-d3b0f38a/demo.html

i cant see icons , and i also put a screenshot it the question if you take a look

What does the inspector show if you check those elements with class "icon-" in the Inspector?

• https://developer.mozilla.org/Tools/Page_Inspector

You can right-click on a web page and select "Inspect Element" to open the Inspector (Firefox/Tools > Web Developer). You can check the font used for selected text in the Font tab in the right pane of the Inspector or click show all fonts to see if Firefox is using the rooeen font.

You can also check the Web Console (Firefox/Tools > Web Developer) for error messages about downloading fonts.

• https://developer.mozilla.org/Tools/Web_Console

I done it, it seems that font is not rendering. please look at screenshots.

Did you check the Fonts tab in the right pane?

You can also check the Web Console for error messages about downloading the font file(s) like I posted above if you haven't done this yet.

i done that console is empty with no errors.

i have no problem in firefox safe mode ! please help to fix this problem :(

If Safe Mode is good, the most likely culprits are one of your extensions or graphics driver incompatibility. To work around the second issue, you can disable Firefox's use of hardware acceleration to see whether that helps.

"3-bar" menu button (or Tools menu) > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

This takes effect the next time you exit and start Firefox up again.

Firefox's Safe Mode also disables style rules you might have created in a userContent.css file, if applicable.

You can try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes
• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

thank you jscher2000 it solved my problem. you made my day :D