[css-fonts-3] Consistent article "an" for @font-face

Author: svgeesus

css-fonts-3/Overview.html

@@ -2453,7 +2453,7 @@ <h3 id=src-desc><span class=secno>4.3. </span>Font reference: the <a
 }
 </pre>
 
-  <p>Just as a <a href="#at-font-face-rule"><code>@font-face</code></a> rule
+  <p>Just as an <a href="#at-font-face-rule"><code>@font-face</code></a> rule
    specifies the characteristics of a single font within a family, the unique
    name used with <code>local()</code> specifies a single font, not an entire
    font family. Defined in terms of OpenType font data, the Postscript name
@@ -5080,7 +5080,7 @@ <h2 id=object-model><span class=secno>8. </span>Object Model</h2>
   <h3 id=om-fontface><span class=secno>8.1. </span>The <a
    href="#cssfontfacerule"><code>CSSFontFaceRule</code></a> interface</h3>
 
-  <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents a
+  <p>The <dfn id=cssfontfacerule>CSSFontFaceRule</dfn> interface represents an
    <a href="#at-font-face-rule"><code>@font-face</code></a> rule.
 
   <pre class=idl>