function openwindow(url, winName, width, height, r, s) 
{
    var xposition=0;
    var yposition=0;
    if ((parseInt(navigator.appVersion) >= 4 )){
        xposition = (screen.width - width) / 2;
        yposition = (screen.height - height) / 2;
    }
    var theproperty = "width=" + width + ","+ "height=" + height + "," + "resizable=" + r + "," + "scrollbars=" + s + "," 
    + "location=0,"
    + "menubar=0,"
    + "status=0," 
    + "titlebar=0,"
    + "toolbar=0,"
    + "hotkeys=0,"
    + "screenx=" + xposition + "," 
    + "screeny=" + yposition + "," 
    + "left=" + xposition + "," 
    + "top=" + yposition; 
    window.open(url,winName,theproperty);
}