When you first visit your web site, you will notice that it does not use default.aspx as the main page.  To change this:

1. Log into your control panel
2. Select the link on the left that represents the domain you want to change the default page for
3. Click the Paper/Hammer icon to the right of "Web Service"
4. Scroll to the bottom of the page.  The next to last line will say "Directory Indexes."  The first time you visit this it will be turned off.  To turn it on, click the "Off" icon.  If it is already on, click the Paper/Hammer icon to the righ.
5. Edit the text box as indicated.

Done