function sobre(id, txt){
	if(document.getElementById(id).value == txt){
		document.getElementById(id).value = "";
		document.getElementById(id).style.color = "#333";
	}
}
function fuera(id, txt){
	if(document.getElementById(id).value == ""){
		document.getElementById(id).value = txt;
		document.getElementById(id).style.color = "#999";
	}
}