Computer science does not equal programming. Yes, programming is a part of computer science but you learn a heck of a lot more from a computer science degree. You learn about algorithms, computational complexity, lots of math, logic and a lot more. You learn how to use a computer to solve hard problems and how to identify patterns in problems that others have already solved. A lot of it is theoretical; you won't be taught how to build a web site.

If you wan't to learn how to program just enough to validate your idea, then perhaps taking a computer science degree might be a little overkill. Read some tutorials and just start programming easy stuff and work your way up.