Is it better for your credit to have several credit cards with moderate limit, or one card with a high limit?

I have zero debt. I also have several credit cards. I am wondering how it will affect my credit to request the highest limit for each card, or if I should cancel all but 2 and have those with high spending limits. Along the same lines, how does "available" credit affect one’s credit score negatively [...] http://bit.ly/me24GL