CSS Quarter Circles

HTML

<div class="quarter-circle"></div>

CSS

.quarter-circle{
     width: 100px;
     height: 100px;
     background: orange;
     border-radius: 100px 0 0 0;
     -moz-border-radius: 100px 0 0 0;
     -webkit-border-radius: 100px 0 0 0;
}