Hi,
I think you should look at captive portals:
http://en.wikipedia.org/wiki/Captive_portalWall'ed' garden is used for permitting guest limited access, which in my opinion, will not be the best thing to have at a public hotspot. More information on the here:
http://www.webopedia.com/TERM/w/walled_garden.htmlhttp://en.wikipedia.org/wiki/Walled_garden_%28media%29There are many software that provide the captive portal functionality. The wikipedia article outlines a few, but you can fins a few more using google (or any other search engine)
Hope this helps.
Warm regards,
Sarang