This page loads an <script src="" /> tag to itself which waits for 5 seconds before responding. This is a simple simulation of a slow response from, for example, external ads served through JavaScript (or perhaps an iFrame - though not tested).
We are expecting to see two 'ready' statements. An alert box will show if DOM wasn't ready when the code tried to run.
Firefox will show the two ready statements. IE7 and Safari will show a failure and only one of the ready statements (executed using jQuery).