function copy() {
var x = screen.width;
var y = screen.height;
var xOffset = (x - 670)/2; 
var yOffset = (y - 500)/2;
window.open('copy.htm','Diapos','status=no,scrollbars=yes,menubar=0,directory=no,toolbar=0,resizable=no,width=670,height=500,screenX='+xOffset+',screenY='+yOffset+',top='+yOffset+',left='+xOffset+'');
}
function clean(){
document.rec.zoom_query.value=''
}