.JS file is called on staging server, not production

I have a button with a javascript call assigned in the code behind:

btnAdd.Attributes.Add("onclick", "javascript:DoAdd('" & ddAddCType.ClientID & "', '" & _
    txtAddCitationNumber.ClientID & "', '" & txtCitRange.ClientID & "', '" & txtCitAmount.ClientID & "')")

The javascript is in a file, that looks something like this:

function DoAdd(typeId, addNumId, rangeId, amountId)
{
 alert('getting here');
    var citType = document.getElementById(typeId).value;

The javascript file is linked in the page like this:

<script type="text/javascript" language="javascript" src="../javascript/CitationFuncs.js">

On the staging server, the javascript function is called.

On production, it is not. I do not get any javascript errors. I have a <div> that contains a loading gif. This shows and disappears normally on both staging and production. But I am only prompted on the staging, not production.

I compared basic settings in IIS on both servers, and both match. The production server folder is set up exactly like the staging server. As far as I can tell, the posting process to both servers is the same. But perhaps I missed something?

How would you troubleshoot this?

Firefox -> Firebug -> Net tab.