>I have a customer where they use several of my ASP.NET applications (it is a large organization with multiple sites). I have always set each ASP.NET application as a separate site. One IT person didn't like it and here is what he did:
>1. He created one site, lets call it 'DmitryApp_Multi_App'
>2. He created a bunch of applications under this site. E.g. "Site1_App", "Site2_app" and so on.
>3. Then when the main page from any of the Sites is to be used (URL) here is way he shows it (and it works):
>
> http://servername.theirorganizationname.org/Site1_app/MainPage.aspx
>
>I can't figure out and hence my question, how and where did he specify the part 'servername.theirorganizationname.org' ?

This requires an entry in a DNS.

As far as running one IIS Web site definition serving multiple Web sites, I have done it for my Web site product. Basically, one Web site serves over 10 Web sites. It just requires some high level parsing at the very debut sequence of the hit to initialize a few things as well as a generic database where each table contains a site primary key. Basically, one directory, one application, one database, but an unlimited number of Web sites.