Popup window

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>