HTML Loading Screen how to ?

Hey dudes,
i was wondering that many servers have their own loading screen if i connect to them. Most of all i think that they are made in HTML but how do i realize to create something like this for my own server ? Like a Rules page while you are connecting or something else ?

thanks !

Step 1. Create an HTML Page that is hosted on the internet somewhere.
Step 2. In your game.cfg add – sv_loadingurl “
Step 3. Enjoy!

Also here’s the wiki page for it sv_loadingurl, it gives the Different JavaScript functions you can access.

Thank you for the fast answer. I alreay searched throgh google but i didn´t know what i should use as search key.