The results I'm seeing from the test page I made are very promising. As it is, I can load my page across several of my devices and effectively have my own CPU mining pool. You'll need hundreds of site visitors to make real money, of course, and you definitely have to check your math, but I'm encouraged.
Here`s a link if you want to try:
https://www.coinimp.com/invite/e15954b7-bbd5-4bd1-a3ab-8f2f633c2081