This is the exact situation I'm in. I'm 18, a high school senior, and am absolutely certain that I want to found a web company. However, I know that were I just to thrust myself into the world right now, I'd always be kicking myself because I didn't have a basic liberal arts education. While a knowledge of philosophy or political history isn't critical to what I will be doing business-wise later in life, I have a feeling that it will be critical to letting me feel like a whole person.
Do what I did - go to college, and spend every free minute working on your project. If you find college doesn't work for you, you'll have a great thing to rebound with.
There's no rush, honest. Starting a company is a big commitment -- a bigger commitment than college in a lot of ways. Your focus will become very narrow and you'll spend 100% of your time on it.
There will be plenty of web companies worth founding three, five, ten, or twenty years from now.
If you'd regret not going to college, go. And if the "founder" bug bites, well, it's not there aren't any example of college startups, right?
