Are you familiar with FaucetHub? All payments are taken care through that microwallet provider. Doing this, you do not have to pay any withdrawal fees on your earnings, it goes straight to there in bitcoin. You don't have to worry about any exchange fees, moving funds from one wallet to another, it's all taken care of via one service. It is especially good for your users since they will be able to request payouts from as little as one satoshi (at your discretion).
Let's say the average user scrolling through your website on a laptop can produce 25 h/s. 25 h/s is 90,000 hashes per hour. WMP pays you 210 satoshi per one million hashes. So, if you were to take a 10% fee from your users from mining, you would pay out to them 189 satoshi per one million hashes. That user would earn ~17.01 satoshi with those current numbers, while you would earn ~19 satoshi from those hashes. After paying out, that's a profit of 2 satoshi. I hope all of this makes sense!
Now, this does not sound like a lot. If you really want to make a decent amount of profit here, you must either have a serious amount of users or charge a higher fee. Or both. Imagine having 7,500 users doing the same thing with a hashrates anywhere from 20 h/s - 70 h/s. Then it starts to add up!
The reason why I recommend WMP is it's easy to setup, has nice features, is transparent, has no fees, and the admin can easily be reached here. He also has another project in the works, FaucetCMS. This is his faucet script we use on Coins4Days.
I will try to answer any questions you have, I hope you hop on board!
