I was hoping someone else would be able to provide a better answer, so I waited. I do know that debian supports both apache version 1.xxx and apache 2.xxx. I think it uses different default documents depending on which version you have installed. Sorry if that is a little vague. You should examine the apache config files and the /var/www area and see if you can understand why you get directed to this page.
In any case, the default pages probably should be removed and replaced with your own site, no?