Traffic is the first factor in alexa rank, the larger, the higher. I think it use the data of times of DNS querying .
Alexa ranking helps to knew about the arrival of traffic to our sites.I hope this link will help you in calculating the alexa rank to your site http://www.alexa.com/siteinfo/
i dont understand why you need calculations for getting your alexa rank...? simply open alexa punch in your website name and bingo... you will get results if you are having any rank or what is your current position....
Nice site, contains most useful information. I found that the content of the site locates at the left most corner of the browser (Firefox 3.5), check it. And also I think there is no need for the menu bar at the both top and bottom of the site because the site looks too short, try to remove any one menu bar..