Through this process, any site has a chance to get listed on any day, and ranking will always be current. If the rankings are completely blank, it must have just reset. Wait 15 minutes or so for the list to grow again. To get listed, a webmaster needs to create an account. If he does that and he filled in all information, he will get the html code he needs to place on his site.
Account number is included.
If my site is down for a couple of days, it no longer shows up on the list. If you brought in less than 2 visitors in the last 24 hours, your site doesn't show up on the list. The account will stay active for 1 month so if you start sending visitors again, your site is listed again. If you take a look at the list, you can already see how the sites are doing. Or just ask someone that is listed how they are doing.