Bulletproof font face

When using @font-face to declare multiple font types for cross browser compatibility, you can see 404's in old versions of IE due to a bug in the way that IE parses the font declarations. For example, this syntax:

@font-face {
    font-family: 'MyFontFamily';
    src: url('myfont-webfont.eot') format('embedded-opentype'), 
        url('myfont-webfont.woff') format('woff'), 
        url('myfont-webfont.ttf')  format('truetype'),
        url('myfont-webfont.svg#svgFontName') format('svg');
}

Will cause a 404 in IE 6, 7, and 8. The fix is to add a question mark after the first font URL, so IE sees the rest of the property value as a query string. This is a correct example:

@font-face {
    font-family: 'MyFontFamily';
    src: url('myfont-webfont.eot?#iefix') format('embedded-opentype'), 
        url('myfont-webfont.woff') format('woff'), 
        url('myfont-webfont.ttf')  format('truetype'),
        url('myfont-webfont.svg#svgFontName') format('svg');
}

Rule Details

Rule ID: bulletproof-font-face

This rule is aimed at preventing 404 errors in Internet Explorer 8 and earlier due to a bug in how web font URLs are parsed.

The following patterns are considered warnings:

@font-face {
    font-family: 'MyFontFamily';

    /* First web font is missing query string */
    src: url('myfont-webfont.eot') format('embedded-opentype'), 
        url('myfont-webfont.woff') format('woff'), 
        url('myfont-webfont.ttf')  format('truetype'),
        url('myfont-webfont.svg#svgFontName') format('svg');
}

The following patterns are considered okay and do not cause warnings:

@font-face {
    font-family: 'MyFontFamily';
    src: url('myfont-webfont.eot?#iefix') format('embedded-opentype'), 
        url('myfont-webfont.woff') format('woff'), 
        url('myfont-webfont.ttf')  format('truetype'),
        url('myfont-webfont.svg#svgFontName') format('svg');
}

This rule requires that the first font declared is a .eot file with a query string, but doesn't check the order of the remaining fonts (which is irrelevant, assuming you have the .eot file first).

This rule was added in v0.9.10.

Further Reading

• The Fontspring Bulletproof @font-face syntax