>When sending a new ASP.NET dll to the server, IIS takes a certain number of seconds before it can use the file. That happens even if the file has already been compiled on the development PC. Can someone explain me why it takes so long to use this new file if it has already been compiled? Or, is there something I am not doing ok?

AFAIK the DLLs will be compiled once again on the server, before it will be used the first time. So the first user has to wait some time before the page appears.