I appreciate that English is not your first language, but this is still a very vague and meaningless question. The core answer is HTTP and TCP/IP I suspect. I also suspect that's not the question you meant to ask. If you write a client/server app you need to write code to connect to the server. Your browser does that for you, obviously, you just need to set up a web host connected to the right URL with the code for a website. Christian Graus Driven to the arms of OSX by Vista. Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.