کد باز شدن پاپ آپ

var _POPUP_FEATURES = 'location=0, statusbar=0, menubar=0, scrollbars=1, width=480, height=640 ,top='+Math.floor((screen.height-640)/2)+' ,left='+Math.floor((screen.width-480)/2);
     
    function isUndefined(v) {
    var undef;
    return v===undef;
    }
     
    function raw_popup(url, target, features) {
    if (isUndefined(features)) features = _POPUP_FEATURES;
    if (isUndefined(target )) target = '_blank';
    var theWindow = window.open(url, target, features);
    theWindow.focus();
    return theWindow;
    }
     
    function link_popup(src, features) {
    return raw_popup(src.getAttribute('href'), src.getAttribute('target') || '_blank', features);
    }
     
    Uso HTML:
    <a href="pagina.htm" onclick="link_popup(this); return false;">Pagina</a>