Postback Failing

I ran into a strange problem this week on a client's .Net site I was working on.  There were two pages where postbacks were being completely ignored.  If you clicked on anything that required codebehind or postbacks to work, such as the login/logout button, the save button, etc., an HTTP POST would occur (verified by Firebug), but the server would ignore the POST and serve up the page as if you did a GET.

Interestingly, it worked great on IE and Safari, but failed on Chrome and Firefox.  What was even stranger was that everything worked properly when debugging in Visual Studio, but the failure occurred when the site was deployed to IIS.

So the failure occurred only when running Firefox or Chrome against IIS.  The same website with IE and Safari worked great, and the same website on Cassini worked great in any web browser.

Hmm...

I ended up using WinDiff to compare the HTML output differences between what was served up from Cassini (Visual Studio during debugging) and IIS.  There was one line that was different:

On Cassini:

<form name="aspnetForm" method="post" action="/default.aspx?" id="aspnetForm">

On IIS

<form name="aspnetForm" method="post" action="/" id="aspnetForm">