Using your website's visitors' CPU to mine for you is an abuse. Some will find out, spread the word and red flag your web (WOT, Google..).
So it will get you nowhere.
Others tried this already on a better light, but I don't think that they've got any result. You can look here, for example:
https://www.reddit.com/r/Monero/comments/57k8n5/mining_monero_in_browser/