function abre_janela(width, height, nome) {
var top; var left;
top = ( (screen.height/2) - (height/2) )
left = ( (screen.width/2) - (width/2) )
window.open('',nome,'width='+width+',height='+height+',scrollbars=no,toolbar=no,location=no,status=no,menubar=no,resizable=no,left='+left+',top='+top);
}

function janelacentralizada(pagina, nomedajanela, w, h) {

 var winl = (screen.width - w) / 2;
 var wint = (screen.height - h) / 2;
 winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+',status=no,scrollbars=yes,resizable=no,menubar=no'
 
 win = window.open(pagina, nomedajanela, winprops)
     
 if (parseInt(navigator.appVersion) >= 4) { 
         win.window.focus(); 
     }

}