function popup (url,h,w){
x=(screen.availWidth)
y=(screen.availHeight)-30
posx=(x/2-w/2)
posy=(y/2-h/2)
winprops = 'height='+h+',width='+w+',top='+posy+',left='+posx+',resizable=no'
win = window.open(url, 'Imatgesc', winprops)
win.close;

  }