Javascript help

I would like to add this code: -moz-border-radius-topright:15px;
Into this code below, somewhere:
if (!sb) {
    sb = document.createElement('div');
    sb.id='statusbar-sb';
    sb.style.display='none';
    sb.style.position = 'fixed';
    sb.style.bottom='0px';
    sb.style.left='0px';
    sb.style.height='1.4em';
    sb.style.width='600px';
    sb.style.background='#aaf';
    sb.style.padding='3px';
    var text = document.createElement('span');
    text.id = 'statusbar-text';
    sb.appendChild(text);
    document.body.appendChild(sb);
}

I tried to add a line called sb.style.-moz-border-radius-topright='3px';
But it doesn't work ;_;

>>1
window['alert'] is the same as window.alert.
in b4 don't help him