function isEmail(email)
{
	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
  if (!filter.test(email))
  {
    return (false);
  }
  return (true);
}

function validateForm()
{
	valid = true;
	
	field1 = document.getElementById("name").value;
	field2 = document.getElementById("email").value;
	field3 = document.getElementById("comments").value;
	
	field1 = field1.replace(/^s+|s+$/g,'');
	field2 = field2.replace(/^s+|s+$/g,'');
	field3 = field3.replace(/^s+|s+$/g,'');
	
	if(field1 == ""){
		valid = false;
		alert("Field 'name' is empty!");
	}
	
	if(valid && !isEmail(field2)){
		valid = false;
		alert("Invalid e-mail address.");
	}
	
	if(valid && (field3 == "" || field3.length < 5)){
		valid = false;
		alert("Please, add some comments.");
	}
	
	return valid;
}