You should indicate in the listings if the particular system/game does not have any available to be sold so that the user doesn't waste clicks. After a couple of dead ends, he'll give up, thinking that none of the entries have sellers.
Also, I tried to make a standing offer for a sega genesis system, but nothing happens when I press Yes to confirm. I'm using Iceweasel 3.0.1 which is essentially Firefox 3.
I clicked Yes, then it asked me to register, so I typed in my info. Then it says check here to agree to the terms and conditions, so I clicked there, and it took me to that page (normally I would have middle-clicked, but I was pretending to be a normal user). So I read the terms and conditions, and when I'm done I want to go back to sign up. So I press back, but my browser pops up saying "Do you want to resend the information?" I press Yes, and all the text I entered is blank.
Possible solution: add target="_blank" to the terms & conditions link.
Also, I tried to make a standing offer for a sega genesis system, but nothing happens when I press Yes to confirm. I'm using Iceweasel 3.0.1 which is essentially Firefox 3.