Additional Comment:
When I put this in the top of my header, it messed up my CSS. If this happens to you, just make sure it's the last line in the header / after the CSS links. Perhaps a CSS master can tell you why (I can't) but that's what I did.
Also, we develop at one domain, and then change the domain when the site goes live. Knowing that, the code I used in the header of index.php was:
<!-- Placed here to make the credit card type dropdown appear in Virtuemart -->
<script language="Javascript" type="text/javascript" src="./includes/js/joomla.javascript.js"></script>
Instead of MYURL, I just put ./
, and it appears to work.
good luck