function pantallaCompleta(pagina) {
window.open(pagina, '', 'fullscreen=yes, scrollbars=yes, toolbar=no, location=no,directories=no,resizable=no,top=0,left=0');
}
function exit()
{ 
window.open('masgalerias_at3.php','salida','menubar=yes,scrollbars=yes,toolbar=yes,location=yes,directories=yes,resizable=yes,top=0,left=0');self.focus();  
}
<!--
var thumb = null;
    function showThumbnail(which,e)
    {
        thumb = document.getElementById('thumb');
        if( thumb && thumb.style.visibility == 'hidden' )
        {
            thumb.style.left       = e.pageX ? pageXOffset + e.clientX + 20 : document.body.scrollLeft + e.x + 20;
            thumb.style.top        = e.pageY ? pageYOffset + e.clientY : document.body.scrollTop  + e.y;
            thumb.style.visibility = 'visible';
            thumb.innerHTML        = '<img src="' + which + '">';
        }
    }
    function closeThumbnail()







    {
        if( thumb )
            thumb.style.visibility = 'hidden';
    }

function MM_jumpMenu(targ,selObj,restore){ //v3.0
  window.open (eval("url='"+selObj.options[selObj.selectedIndex].value+"'"));
  if (restore) selObj.selectedIndex=0;
}
//-->
function theDay(dOff){
  aDay = new Date();
  aDay = new Date(aDay.setDate(aDay.getDate()+dOff));
document.write((aDay.getDate())+"-"+(aDay.getMonth()+1)+
        "-"+(aDay.getFullYear()+"").substr(2));
}