If any of your photos are crooked, you can use iPhoto to straighten. To straighten a photo in iPhoto, double-click on it in the Viewing area to open it in edit mode. Next, click on the Adjust button to open up the Adjust pane. You can then use the Straighten slider to gradually rotate your photo until it is no longer crooked. You can also use the buttons on either side of the slider if you want to be more precise. A grid will be display when you begin to straighten your photo. You can use the grid to guide you as you rotate the photo until it is straight.