Style width:100%;height:100% is not working in IE6.0

#backgroundPopup{
position:absolute;
height:100%;
width:100%;
}

its fine, if we give width=500px; but when we put as % then no 开发者_开发问答result. In IE6.0 Why?

---

try setting this in addition

html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
}