Edit style.css (line 288) and change:
.side1 h2, .side2 h2 {
-x-system-font:none;
background:#6F7374 url(images/bg-dark.gif) repeat-x 0 0;
color:#FFFFFF;
font-family:Georgia,"Times New Roman",Times,serif;
font-size:1.2em;
font-size-adjust:none;
font-stretch:normal;
font-style:normal;
font-variant:normal;
font-weight:normal;
line-height:normal;
margin-bottom:5px;
padding:4px;
text-transform:uppercase;
}
to:
.side1 h2, .side2 h2 {
-x-system-font:none;
background:#6F7374 url(images/bg-dark.gif) repeat-x 0 0;
color:#FFFFFF;
font-family:Georgia,"Times New Roman",Times,serif;
font-size:1.2em;
font-size-adjust:none;
font-stretch:normal;
font-style:normal;
font-variant:normal;
font-weight:normal;
line-height:normal;
margin-bottom:5px;
padding:4px;
text-transform:uppercase;
text-align:center;
}
(Added text-align:center;
)