A millihelen is a standard unit of beauty, equal to 1/1000th of the beauty of Helen of Troy, who (mythologically) is the most attractive woman who ever lived.
Since Helen was also the "face that launched a thousand ships", one millihelen is also the amount of beauty it takes to launch one ship to rescue you if you are abducted by a Trojan prince.
A picture must be rated 10 times before it is assigned a score. The ranking system needs a few comparisons before it can assign an accurate score.
The simple explanation is that the score in millihelens (abbreviated mH) is related to the win/loss ratio of the picture, but also dependent on the scores of all the other pictures. The complicated explanation is that the site places all of the pictures on a normal distribution and assigns scores based on distance from the mean.
My friends and I were at a restaurant one day, and happened to have a really hot waitress. We were trying to rate her from 1-10, and we couldn't agree since the scale was too arbitrary. I thought the waitress was a 7, but my friend thought she was a 9. We started arguing, and the argument snowballed into this website.
Copyrighted images and pictures with nudity (or almost nudity) are not allowed. Let's keep the site real and clean. I also reject small pictures, because they show up really grainy (and therefore get unfairly low ratings).
Remember that the quality of the picture usually affects the score it receives. To maximize your score, try and make sure that at least the upper half of your body is in the picture. If the picture contains multiple people, make it clear which person is being rated. Remember to smile.