When you think you are finished the editing process, add a white border, or resize the canvas by 50 or 100 pixels around. What this does is gives you a view of how your photo will look when placed against a white background. Often times, by doing this, you will see background areas that were missed. For example:

I hope this quick tip was helpful, so you may have the best pictures possible for your website!
~Kirsten
P.S. - no arrows were injured in the making of this image