GoLive has the feature called a "Grid" which allows you to move items with pixel-pefect precision. Coming from a print design background, I thought this was great -- it worked just like Quark or Illustrator -- until I learned HTML and realized that each time I "bumped" something up or down a pixel, it created spacer columns and a mess of nested tables. (I no longer use GoLive.)
If you decide to tell him "his work is terrible" as you put it, then I'd suggest that you stick to the objective items. For instance, show him how he can shrink that 350K jpeg down to 20K.
I wouldn't critize his design style, since that's subjective. But if you can demonstrate how it affects the user's experience from a usability standpoint, then you have a case to make.