If you wanted to make it "invisible" to the average user, you could use frames, the left frame being nearly invisible and the right being the rest of your content. The address bar would stay the same no matter what was clicked in the right frame. such as:
<frameset framespacing=0 cols="1,*">
<frame name="left" src="some blank page" scrolling="no" frameborder="no">
<frame name="right" src="your data" scrolling="no" frameborder="no">
</frameset>
Use this in combination with the javascript status bar and most people won't know the url. Of course the smart ones can check the source.