if you're primarily doing web design/coding, i'd say that the most important factors are that you have a high resolution and lots of ram. mainly because you'll be having a lot of applications open at once. cpu and gpu aren't as important because you're just going to be viewing websites. optionally, an ssd is a nice addition as it'll make your laptop practically invulnerable to drop damage, and also your OS will boot a lot faster.
i'd aim for something with these specs:
ram: at least 8gb
resolution: at least 1680x1050
cpu: at least a dual core
storage: ssd with at least 100gb
battery life is also an important consideration. generally the more powerful your other components are, the less battery life you're going to end up with. how relevant this is depends on how often you'd be working on the go vs plugged into an adapter.
