function make_popup(url, width, height, overflow){
	  if (width > 655) { width = 655; }
	  if (height > 480) { height = 480; }
	
	  if (overflow == '' || !/^(scroll|resize|both)$/.test(overflow))
	  {
		overflow = 'both';
	  }
	
	  var links = (screen.width - width)/2;
	  var boven = (screen.height - height)/2;
	
	  var win = window.open(url, '',
		  'width=' + width + ',height=' + height + ', left=' + links + ', top=' + boven
		  + ',scrollbars=' + (/^(scroll|both)$/.test(overflow) ? 'yes' : 'no')
		  + ',resizable=' + (/^(resize|both)$/.test(overflow) ? 'yes' : 'no')
		  + ',status=no,toolbar=no,menubar=no,location=no'
	  );
	
	  return win;
}

window.addEvent('domready',function() {
// process 'external' links	
	var t = $$("a[rel=external]");
	t.each(function(lnk, nr){
		lnk.set({'target':'_blank'});									
	});	
	
});