Lining up images

From: Samson


Hi, I'm new to photoshop. Thank you for this site. I'm trying to convert a picture I made into a web background. It's an inverted L, and I want to divide it into three sections, menu, lefttop, and righttop. I'm having trouble lining them up though (not in the code, when I'm cropping in PS). Is there a way to show pixels in PS or to select and crop several rectanges at once? Thanks for your help.