How to let a client pc response to a query

Well, i know the title isnt what i mean but thats the problem. i know what i want, but i dont know how its called. else i could just do some googling....
anyway, what i want is a website to send a special URL witch activates a service on the clients computer, so with http://woot.com, your default browser is automaticly started. with mailto:[email protected], your default email client is automaticly started. how can i create my own, so with for example: eye:\\localhost:1003 my written client will be activated....

Thanks already!

For Windows Internet Explorer, this is called a asynchronous pluggable protocol.

thanks, i can work my ways with that :)