Prusak.com

One of the limitations of using a standard A/B split test is that it won’t work out of the box if the page you are testing is the “action” page for a form that uses method=POST.

For example, lets say you have a simple form page – form.html that looks something like this:

Address <input type=text name='address'>

You’ve created process_form_2.php to split test against process_form_1.php.

The problem is that when process_form_1.php redirects to process_form_2.php, you will have lost all of your form data since your form uses POST.

There are two solutions for this:

1. Switch from method=POST to method=GET.
If this is an option, it’s probably the easiest solution.

2. Setup the experiment as a multivariate experiment and change the form action line in the HTML.
For example:

<script>utm_section('form action')</script>

</noscript>

and then in the experiment setup, add a variation like this:

<form action='process_form_2.php' method='POST'>

Hope this helps.
Ophir