It doesn't matter if you do all the error checking in the world, or if you have the most beautiful graphics, if your site or application design isn't usable, it's not going to do well. Get input and advice on usability and user interface issues here.
God you guys must sure enjoy criticizing others. There's nothing wrong with constructive criticism but I had to look hard for 1 positive comment about his web site. It's not a sin to tell someone they did a good job. I think his site looks great and it's definetly better than the "enemy".
How can you judge something without looking at the source code? Clearly the first site doesn't update inventory when you change the date, not very professional. One of the main goals is to manage inventory.