The contents below are two pages loaded in a hidden iframe one by one, then copied into the main page, with your users none the wiser. Go to "view source" at the bottom under "Page Information." The lines in the script relevant for changing are:
<div id="stuff"></div>
...
...
...
pages[0] = new Array("Music?raw=bare","stuff");
pages[1] = new Array("Poetry?raw=bare","stuff");
The first line defines a container element. The subsequent lines define a loaded page, the first field being the URL and the second field being the id of the container. If you define the same container, it appends to the previous data.