The thing is, there's no such thing as "website design centric" techniques in Photoshop, except maybe the effects palette (but you can learn 90% of that just by playing around with the options).
The effects palette aside, all you need for web design is the typographic tools, vector shapes, and rulers (to set up your grid). So you can basically learn the technical aspect of "Photoshop for web design" in 30 minutes.
The thing is, there's no such thing as "website design centric" techniques in Photoshop, except maybe the effects palette (but you can learn 90% of that just by playing around with the options).
The effects palette aside, all you need for web design is the typographic tools, vector shapes, and rulers (to set up your grid). So you can basically learn the technical aspect of "Photoshop for web design" in 30 minutes.