Q:

how do I add an option to a html form dropdown list with javascript

I want this script to add an option to the list.
When you open the list I want the options to be test and hello
What am I doing wrong? 
<SCRIPT>
function runList(){
    document.getElementById('list').value = "<option>hello</option>";
}
</SCRIPT>

<FORM NAME="myform" ACTION="" METHOD="GET">
Your Options:
<INPUT TYPE="button" NAME="button" VALUE="Click" onClick="runList()"/>
<SELECT NAME="list" ID="list">
<OPTION>test</OPTION>
</SELECT>

A:

You need to actually add the option object to the dom. I have linked to a fiddle with your example working: http://jsfiddle.net/DS8TG/
Change runList to the following:
function runList(){
  var select = document.getElementById('list');
  select.options[select.options.length] = new Option('Hello', 'Hello');
}​

A:

try out this 
var element = document.getElementById('list');
element.options[element.length] 
   = new Option('yourText', 'yourValue');

