DLL's are created when the site compiles.

You will notice that all your code behinds and also Class's have now gone.

These are now.

System.Data.dll
System.Data.OracleClient.dll
System.EnterpriseServices.dll
System.EnterpriseServices.dll
System.EnterpriseServices.Wrapper.dll
System.Transactions.dll
System.Web.dll

And it is very important that they remain with the site for it to functaion.

Regards