How do you deal with haters?

Having a bit of a web presence, I’ve found myself the victim of a bunch of personal attacks by a group of people who clearly have a lot of time on their hands. I’m not sure how to handle the situation. Acknowledge them or ignore them? I thought I’d extend the question to offline as well, and see if you guys have some advice on the best way to handle negative feedback and criticism (especially when it’s unconstructive!)