A-vs-B is an image discovery game. The game displays a pair of images which have a similar ranking score, and you can then vote for the image you think is best. You can make your decision based upon whatever criteria you like, the image you vote for may catch your eye first, it may be the best one technically, or it may not be but it looks the coolest - its all about which image you prefer and so there are no rules!
When you vote for an image, its ranking score is increased, and the other one is decreased, and over a period of time the best images will "rise to the top".
Every image has an A-vs-B ranking. The score is calculated based upon how many times the image has "won" a vote, "lost" a vote, and how many times it has appeared in a pairing.
Images with a higher win/loss ratio will ultimately have a higher ranking, and those with a low win/loss ratio, will have a lower ranking.
Sorry! We're keeping all voting anonymous, we want all voting to be focussed solely on the images themselves :)
Don't worry, your image may not have been paired in the game enough times yet - give it a little while, and check again.