If thats true, and I don't believe it is, that only shows how far US standards are from the rest of the world. Anyone with such an agressive foreign policy as Kerry-Edwards, that embodies traditional liberal values (abortion, gay marriage, environment, social programs) to such a slight degree, can hardly be called liberal. If Kerry is liberal, then that word (as interpereted today, not the classical definition which is quite different) is meaningless.
I believe the website accurately charts the position of various politicians on the scale. Its only if you have certain pre-concived notions about who is what, mostly unscientific, that you will try to fight against it. They (the website) uses voting records, just about the most accurate source of data available.