Make Adobe fonts work with CSS3 @font-face in IE9

Question

I can only explain you how to fix the "CSS3114" error.
You have to change the embedding level of your TTF file.

Using the appropriate tool you can set it to installable embedding allowed.
For a 64-bit version, check @user22600's answer.

As Knu said, you can use this tool, however it's compiled only for MS-DOS. I compiled it for Win64. Download.

Usage:

1. Place the .exe in the same folder as the font you need to modify

2. Navigate to that directory in the command line

3. type embed fontname.fonttype, replacing fontname with the filename and fonttype with the extension i.e. embed brokenFont.ttf

4. All done! Your font should now work.

You should set the format of the ie font to 'embedded-opentype' and not 'eot'. For example:

src: url('fontname.eot?#iefix') format('embedded-opentype')

I was getting the following error:

CSS3114: @font-face failed OpenType embedding permission check. Permission must be Installable.
fontname.ttf

After using the below code my issue got resolved....

src: url('fontname.ttf') format('embedded-opentype')

Thank you guys for helping me!
Cheers,
Renjith.

Try this, add this lines in the web.config.

<system.webServer>
  <staticContent>
     <mimeMap fileExtension=".woff" mimeType="application/octet-stream" />
  </staticContent>
</system.webServer>

A Different Answer: Legal issues.

There's a couple of things to note before you do this. First, to get this error, in IE, inspect element, switch your tabs, and look for the errors, I believe "CSS3114" appears in the console.

What you need to understand is this is a licensing issue. I.E. (pun intended) if you are trying to load a font that causes this error, you don't have permissions on the file to use the font, and if you don't have permission, it is highly likely that you may lose a legal battle (which itself is highly unlikely) over using this font in this manner unless you are holding the license. So, you can, for the first time, thank IE for being the only browser to tell you "no", because it at least lets you know that you are doing something questionable.

That said, here is your answer:

First ensure you're using the best code in .css, see some of the other css answers for that.
IE 11 css example (works in all modern browsers may need to be tweaked for IE9):

@font-face {
font-family: "QuestionableLegalFont";
font-weight: bold;
src: url('../fonts/QuestionableLegalFont.ttf') format('truetype');
}

Then, ensure you have a working web-font (you probably already know this by seeing your font in other browsers). If you need an online font converter, check here: https://onlinefontconverter.com/

Finally, To get rid of the "CSS3114" error. For an online tool, click here: https://www.andrebacklund.com/fontfixer.html