function centrePopup(theURL,winName,width,height,features) {
    var cTop = (screen.availHeight/2) - (height/2);
    var cLeft = (screen.availWidth/2) - (width/2);
    window.open(theURL,winName,'width='+width+',height='+height+',top='+cTop+',left='+cLeft+features);
}