var popWin = "";
function openwin(url, strWidth, strHeight) {
if (popWin != "") {popWin.close()}
leftStr = (screen.width-strWidth)/2;
topStr = (screen.height-strHeight)/2-50;
windowProperties = "toolbar=no,menubar=no,scrollbars=yes,statusbar=no,height="+strHeight+",width="+strWidth+",left="+leftStr+",top="+topStr+"";
popWin = window.open(url,'newWin',windowProperties);
}