Why getURL stops browser back button from working ..? (firefox, safari)

Here is the site. http://initiatie-initiatief.net/
It is in Dutch language but I think that doesn't matter too much it is all quit logic.
They all are html pages with each their swf.
In the flash is a menu on the right. Every row is another menu link.
The links on the flash have:

on (press, release) {
getURL("example.html","_self");

}

The thing is that the links all link to an html page with a swf (they look all pretty much the same so this is not easy to see and btw not logic but that is an other subject..)
So when you use the menu say you click one after another the first three menu items, one would expect the browser to have that in it's memory and I thought the back button of the browser would work. But not. Not in Firefox not in Safari. How is this possible
Also the <title>title</title> does not change in the browser also not when another html page with another title is loaded..

Help! How is it possible?