The current mozilla trunk does not support svg fonts. See
http://www.mozilla.org/projects/svg/status.html and bug 119490. When
it does you would be able to put svg text which used svg fonts in
xhtml documents. xhtml text would not be able to use svg fonts
directly and you will not be able to do this with HTML documents at
all as you can't put svg in them.
To embed you would do something like this:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title/>
</head>
<body>
<svg xmlns="xmlns="http://www.w3.org/2000/svg">
<font id="Font1" horiz-adv-x="1000">
<font-face font-family="Super Sans" font-weight="bold" font-
style="normal"
units-per-em="1000" cap-height="600" x-height="400"
ascent="700" descent="300"
alphabetic="0" mathematical="350" ideographic="400"
hanging="500">
<font-face-src>
<font-face-name name="Super Sans Bold"/>
</font-face-src>
</font-face>
<missing-glyph><path d="M0,0h200v200h-200z"/></missing-glyph>
<glyph unicode="!" horiz-adv-x="300"><!-- Outline of exclam. pt.
glyph --></glyph>
<glyph unicode="@"><!-- Outline of @ glyph --></glyph>
<!-- more glyphs -->
</font>
</defs>
<text x="100" y="100"
style="font-family: 'Super Sans', Helvetica, sans-serif;
font-weight: bold; font-style: normal">Text
using embedded font</text>
</svg>
</body>
</html>