Mymonero charges a fee for each transaction sent from the webwallet? What exactly is that fee and how is it calculated?
50% on top of the miner fee, so the old fees were 0.01 XMR per kb, and if you used MyMonero it was 0.015 XMR per kb. With the new fees it's 0.002 XMR per kb, and 0.003 XMR per kb with MyMonero. We also have an algorithm to turn the fee off once we've covered our monthly hosting costs, but that's never happened:-P