How to embed css in xml?

I am trying to apply an embedded bar-code font from my css to an xml file. The xml file produces order numbers that I need to display as bar-code.

This it what generates order numbers:

   <font face="barcode">
                <xsl:value-of select="$OrderInfo/OrderNumber" />

              </font>

I've tried linking my css using both:

<?xml-stylesheet type="text/css" href="App_Themes/Skin_3/style.css" ?>

<link href="App_Themes/Skin_3/style.css" type="text/css" rel="stylesheet"/>

Embedded font in css:

@font-face {
    font-family: barcode;
    src: url(Fonts/IDAutomationHC39M_FREE.otf)  format("truetype");
}

barcode
{
    font-family:barcode; 
     font-size: 26px;
    font-weight:normal;
    }