No offense to anyone, but heres the info you need.
I created my own web interface to control XBMC. I saw alot of great interfaces but they were to heavy for the older 10" tablets I use for custom home control. Heres the thread if you want to take a look.
http://forum.xbmc.org/showthread.php?tid=50589
I will not go into actually creating a website interface I am sure if you want to do this you know what you are doing. IMO it is sometimes better to reinvent the wheel if the wheel doesnt fit. Imagination is the fuel of invention.
To add your website interface to XBMC:
Whatever site you create just add a addon.xml file into your site folder and then zip the folder. Goto addons in the system menu and you should see a install from zip. Locate your zipped site folder and you should see a message that confirms your file was added. Now goto your system network setting and change the interface to your creation. Restart XBMC ! if all goes well you should be able to open a browser , enter ip for XBMC and your interface will load.
Let me know if you need the contents of the xml file as an example, I searched and found a few examples.
Hope this info helps you.