html listbox

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<select id="list" onclick="validate();">
    <option VALUE="A">mushrooms</option>
    <option VALUE="B">green peppers</option>
    <option VALUE="-">onions</option>
    <option VALUE="C">tomatoes</option>
    <option VALUE="D">olives</option>
</select>

JavaScript

function validate(){
  var sel = document.getElementById("list"); 

  for (var i = 0; i < sel.length; i++) {
    var opt = sel[i];
    if(opt.value=="-"){
      alert(opt.text);
      opt.setAttribute('disabled', 'disabled');
    }
  }
  return true;
}