[gold stinger]

average rank is based on your placement/rating across all public songs

grand total rank is based off of just that, grand total that is shown in the top-right of the webpage. A sum of all scores accumulated.

skill rating is based off of PA Value and a weight system designed to highlight your best obtained scores in the game. You can overview your specific scores at this URL, along with the imposed weights on how well the score is compared to others. It updates from time to time, but if you think you have way better scores or think the system is just not updating, you can visit http://www.flashflashrevolution.com/leaderboards/ and click the green refresh icon next to where it says "useme99999's Dashboard" to manually update it.