The worst and most common boxing mistakes especially in beginner fighters. I would see the main fighting mistakes are the cause of all the other boxing mistakes when it comes to forgetting techniques, or bad stance. The problem with these mistakes is that it leads to poor technique, slow development, or otherwise somehow gets in the way of you learning how to box properly.
Check out "How to Box in 10 Days"
(my highly regarded boxing instructional EBOOK & VIDEO):
This video is hosted from www.youtube.com