function getRef(id) {
		return (document.getElementById ? document.getElementById(id) : document.all[id]);
}

function showElements() {
			 if (document.getElementById) {
					 var howManyNum = getRef('howMany').value
					 for (i=6;i>0;i--) {
					 	document.getElementById('age' + i).style.visibility='hidden';
					 	document.getElementById('age' + i).style.display = 'none';
					 }					 
					 for (i=howManyNum;i>0;i--) {
						 document.getElementById('age' + i).style.visibility='visible';
						 document.getElementById('age' + i).style.display = 'block';
					 }
				 }
			}