edit site description- i can change size & placement but not font?

hi i have a twenty-ten theme
ive created a child theme and a stylesheet

but i cannot override the font style in my stylesheet, it allows me to change size amongst other things but not the font type. can someone help me please? these has been troubling me for a week now.

#site-description {
clear: left;
float: centre;
font-style: none;
font-family: georgia;
margin: 10px 0 5px 0;
width:900px;
font-size:20px;
color: #444;
}

site- calligraphycompany.com

thanks
olivia