Each ASP.NET application is automatically configured to look in the \bin subdirectory, located immediately under your application root, for the required .NET assemblies. By default, the root of your site is an application. Remember, you can create more than one application on your site using certain tools such as Visual Interdev or Visual Studio .NET. Each application would need its own \bin directory. If you are using Visual Studio .NET, your application (and its \bin directory) will be created automatically when you create a new Web project in a subdirectory of your site.