function openCenteredWindow (sAddress, sName, iWidth, iHeight, sParams) {
    leftVal = Math.floor( (screen.width - iWidth) / 2);
    topVal 	= Math.floor( (screen.height - iHeight) / 2);
    var winParms = "top=" + topVal + ",left=" + leftVal + ",height=" + iHeight + ",width=" + iWidth;
  	 if (sParams) { winParms += "," + sParams; }
  	 var win = window.open(sAddress, sName, winParms);
    if (parseInt(navigator.appVersion) >= 4) { win.window.focus(); }
    return win;
}