In html-reset.css, Tahoma is the first font on line 78:
font-family: Tahoma, Verdana, Arial, Helvetica, "Bitstream Vera Sans", sans-serif;.
This contradicts the comment stating that you are using "Microsoft core web fonts." In fact, Tahoma was designed in 1994, which is pre-web for Microsoft.
I recommend dropping Tahoma entirely. It wasn't designed for the web and just looks wrong, especially with its unpleasant italics. Use Calibri instead.