<p>Has anyone encountered the following problem: I have IIS7 running on my computer. On that same computer, I open IE7 and the website works (<a href="http://localhost/web.site/Default.aspx" rel="nofollow noreferrer">http://localhost/web.site/Default.aspx</a>). Put that same url in Firefox 3 and I get the welcome screen of IIS7, a big image with IIS7 in the middle and 'Welcome' in several different languages. Clicking on the image leads you to <a href="http://www.iis.net/" rel="nofollow noreferrer"><a href="http://www.iis.net/" rel="nofollow noreferrer">http://www.iis.net/</a></a>.</p>

One browser accesses your server via 127.0.0.1, and another via your external IP.
Make sure virtualhost works with all network interfaces.