So I've been playing guitar for about 4 years. I can play pretty well. With the picking hand, I have no problem at all, but with my fretting hand, I'm not so well. My fingers just sometimes don't keep up with the pick. In other words, they are slow for some riffs. Could there be anything wrong I'm doing? Is there any website that explains what things you could be doing wrong and how to improve your fretting hand?

Practice would be great. Trust me... I was...well still am in the same boat. I've got a lot better, but just practice.
Gear List

Gibson Les Paul Standard
Jackson KingV
Oscar Schmitt OE30

Orange Rockerverb 50
Marshall Mode Four

Gas List
Gibson Firebird