function setFocus(aField) {
	document.forms[0][aField].focus();
}

function isEmpty(aTextField) {
	if ((document.forms[0][aTextField].value.length==0) || (document.forms[0][aTextField].value==null)) {
		return true;
	} else { 
		return false; 
	}
}

function es_nulo(variable) {
	if ( (variable.length == 0) || (variable == null) ) {
		return true;
	} else {
		return false;
	}
}