I think learning designing is more important than learning Photoshop, because it's just a tool.
I recommend you to watch some play by play from peep code. Since I watched them I understood the process to design a good UI:
I recommend you to watch some play by play from peep code. Since I watched them I understood the process to design a good UI:
I'd recommend tackling both design theory and Photoshop techniques, unless your only interest is in implementing other people's design work and you just need to know Photoshop techniques to translate that work from PSD to HTML/CSS.