function Ventana_Descarga(mypage, myname) {
	var w='400';
	var h='250';
	var winl = (screen.width - w) / 2;
	var wint = (screen.height - h) / 2;
	winprops = 'location=0,menubar=0,resizable=0,scrollbars=0,status=0,titlebar=0,toolbar=0,height='+h+',width='+w+',top='+wint+',left='+winl;
	
	win = window.open(mypage, myname, winprops)
	if (parseInt(navigator.appVersion) >= 4) { win.window.focus(); }
}

function checkPw() {
    validity = true;
    if(!check_empty(document.form.username2.value))
    	{validity = false; alert('Introduce tu Nombre de Usuario');}
    if(!check_email(document.form.email2.value))
        {validity = false; alert('La dirección de E-Mail es incorrecta');}
    return validity;
}

function check_empty(text){
    return (text.length > 0); //returns false if empty
}

function check_email(address){
    if((address == "") || (address.indexOf('@') == -1) || (address.indexOf('.') == -1))
       return false;
    return true;
}