SO fiddle

Test Fiddle mainly for SO Questions

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<div id="progressbar"></div>

CSS

#progressbar .caption { width: 50px; margin: 0 auto; }

JavaScript

$("#progressbar").progressbar({
    value: 37
}).append("<div class='caption'>37%</span>");