function checkdata() { 	
	
	if (document.formcontacto.email.value.length == 0) {
		alert("Por favor, indique un email de contacto");
		document.formcontacto.email.focus();
		return false;
	}
	document.formcontacto.submit(); 
}

function showImg(imgname, rollname)
{
	if (document.images) {
		window.onerror = null;
		document.getElementById(rollname).src=eval(imgname + ".src");
	}
}