Cusomize website to view on smart phones(repost)

I owe a website: [login to view URL] which should be changed to accommodate users which want to see it from smartphones. Basically website should identify if user opens it from PC/MAC or from smartphone and redirect user to appropriate pages. I want to preserve all current site options for mobile version also, however I do not mind changing the design, like to have a list of all options listed one after another to be able to see all of them on small screen.