What extra do I have to do in my HTML/PHP coding to display my webpage on mobile browsers??
Is it possible to display website on mobile w/o coding it for WAP ?

What's the URL to the website you want to be compatible with mobile browsers?

A simple solution is just to provide an alternate CSS stylesheet for handheld devices. A great article on this is at A List Apart.
http://www.alistapart.com/articles/pocket/

If you've got a simple site like mine (in signature), you get your contents displayed neatly in one colum (if you select that function).

Yes, it's also wise to include another CSS optimised for pocket devices.