Question

I have a web app that works fine from all browsers (IE9, Firefox, Chrome, Opera & Safari) on my development machine . When I deploy the web app to a test server, IE will start to choke on a particular javascript component (Zoomify).

I can have IE 9 open with the dev hosted web app in one tab and the test server web app in another tab and only the dev hosted app will work. The web app code is exactly the same on both machines, except for the web.config.

The Developer Tools show both sites as being in Browser Mode: IE9 Document Mode: IE9 standards.

The Zoomify component is failing on the following line:

c.onreadystatechange=null

with the error:

SCRIPT13: Type mismatch

What is going on here? Why is IE behaving differently with how it processes Javascript depending on where the web app is hosted?

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Update

I’ve now tested on another server and strangely enough it is working. At this point, the situation is that when the web app is hosted on IIS 6, the javascript file will fail in IE.

A similar issue exists in Opera, but I do not get an error message.

Dev Machine
Windows 7
Web Server: Cassini
Status: Working

Test Server 1
Windows Server 2003
Web Server: IIS 6.0
Status: Not working

Test Server 2
Windows Server 2008
Web Server: IIS 7.0
Status: Working

Answer 1

The failing javascript line c.onreadystatechange=null was misleading. Through debugging the Zoomify javascript code, I was able to determine that an error was being generated further up the call stack.

The Zoomify component was attempting to download images for display and was failing due to IE not supporting cross domain calls over the XMLHttpRequest object. IE does support cross domain calls using the XDomainRequest object. However, the Zoomify component does not provide support for XDomainRequest. Opera 11 does not support cross domain calls either.

My workaround for the problem with IE & Opera was to not use cross domain calls and to make the image resources available via a URL on the same domain as the web app.