When you're writing an application to run on multiple domains, but using a single copy of code, the first thing you have to work out is your Web Server Configuration. Basically there will be a DNS entry for each domain pointed to your server's IP Address. Then your web server will have to be configured to handle those domains. Rarely, in an MSOC environment, will you need a separate site entry for each site you're serving, requiring one entry to serve all sites. If you're working with IIS on Windows you could just use the Default Web Site entry in your IIS manager. Apache is a little different.