var popupwindow = null;
var offsetx = 0;
var offsety = 0;

function popup(webpage,name,offsetx,offsety) {
        if (window.screen) {
        var horizontal = screen.availWidth;
        var vertical = screen.availHeight;
        popupwindow = window.open(webpage,'name','scrollbars=yes','width='+ offsetx  +',height='+ offsety +',left='+((horizontal - offsetx- 10)* .5) +',top='+((vertical - offsety- 30)* .5));
        popupwindow.focus();
}
}