Yeah so fix it? If a site fails the validation there are obviously a few errors needing fixing. If you have a paypal button most likely that, otherwise just look at the description and change them and try the validation again. My suggestion is to re-validate it every time you think you fixed one. This way if you get it wrong you can tinker with it, instead of doing 50 or so then forgetting the errors of the still not fixed onces.
Webpage failing W3C Validation
Linear Mode
