Just use spans in the middle of your a
tag:
<style>
a#logo .oneFont { font-family: sans-serif; }
a#logo .twoFont { font-family: Arial; }
a#logo .redFont { color: red; }
a#logo .blueFont { color: blue; }
</style>
<a id="logo" href="#">
<span class="oneFont">LogoWith</span>
<span class="twoFont">TwoFontFamilies</span>
<span class="redFont">AsManyAsYou</span>
<span class="blueFont">WantToUse</span>
</a>