Possible Duplicate:

Use created attribute with javascript in select list

im trying to access an attribute that i created in a select list.

<script language=JavaScript>

function updateUrl()

    {

        var newUrl = document.getElementById('test').getAttribute('car');

        alert(newUrl);

    }

</script>



<select name= test id= test onChange= updateUrl()>

     <option value=1 selected=selected car=red>1</option> 

     <option value=2 car=blue >2</option> 

     <option value=3 car=white >3</option> 

     <option value=4 car=black >4</option>    

</select>

it keep giving me null. how do i get the value from attribute car?