Prusak.com

When running an A/B experiment Google Website Optimizer appends any parameters from the original page when redirecting to one of the test pages.

For example, the original page is index.php and the test page is index2.php.
If a user clicks on index.php?name=fred they will be redirected to index2.php?name=fred

So what happens if the test page URL already has a query parameter in it?

For example, the original page is index.php and the test page URL is index2.php?section=b
What will happen if the user clicks on index.php?section=d ?

About seven months ago I had a client with this exact scenario so I tested it.
The user was directed from index.php?section=d to index2.php?section=b&section=d
I found a work-around and didn’t think about it after that.

A few weeks ago I found out that Google was indeed aware of this “issue” and fixed the GWO code 🙂
Now GWO will merge the parameters from the two URLs, not just append them. The parameters defined during setup for the test page URL will get precedence over the parameters from the URL the user clicked on.

For example, the original page is index.php and the test page URL is index2.php?section=b
What will now happen if the user clicks on index.php?section=d&cat=22 ?

They’ll be redirected to index.php?section=b&cat=22

This doesn’t effect 99.99% of all A/B tests, but if it does effect you, Google’s fix is a life saver 🙂

I’ve been doing a lot of reading on the Google Website Optimizer help pages:
http://www.google.com/support/websiteoptimizer/

For the most part, the help pages are kept up to date, but every now and then something falls between the cracks and I get the feeling the page does not reflect the latest updates.

I was just thinking how every Google help page should really have a time stamp, letting readers know when the page was first created and when it was last updated.

Something like:
This page was created on Sep 20th, 2007 and last updated Oct 24th, 2008.

Any thoughts?

Google Website Optimizer A/B experiments use JavaScript to redirect the visitor to a test pages.

When a visitor is redirected with JavaScript, you loose the original HTTP referer data (the page that did the redirecting now becomes the HTTP referer)

Here’s an example:
Lets say the original page is page.html and we have a test page page_1.html

Before the test, page.html got 1,000 visitors a day coming from Google searches (organic traffic).

So we have Google -> page.html

Now that the test is running you’ll have 500 visitors to page.html:
Google -> page.html

and 500 to page_1.html
Google -> page.html (JavaScript redirect) -> page_1.html

If the web analytics code is after the redirect on page.html (which is what Google tells you to do) then data based on the HTTP referer will be incorrect (traffic source, keywords, etc).

If you REALLY want to capture the HTTP referer related data you can put the analytics code before the redirect. You’ll now be able to capture the original HTTP referer data, but you’ve also just inflated the page views.

I’ve solved this issue for some in-house code that uses the referer data by simply storing the HTTP referer value in a cookie right before the redirect, and then using the cookie value on the test page.

Unfortunately Google Analytics doesn’t do this.

Here’s a feature request for the Google Analytics team:

Add a way pass in the HTTP refer data manually.

I’m sure Website Optimizer isn’t the only tool using JavaScript redirects from a landing page.