Photo Formats

I am cropping my photos in cs3, and saving them as a jpeg.  I am cropping them at the correct ppi, but then save them as a jpeg file. 

When I have them in my column of photos to import, the jpeg dimensions are totally different….are these photos still going to fit Ok?  This is my first book and I’m sooo worried my photos are going to look like works of abstract art.   HELP !