If I am not mistaken, MoonBTC is a Bitcoin faucet, correct? It's been a while since I used those. They are an absolute waste of time to earn anything. They were just there in the early years to let people test out Bitcoin with some negligible amounts, just so they can see how it works. Nowadays you have Bitcoin exchanges and the Bitcoin fees are way to high to make transactions from faucets.
Please note that this has nothing to do with mining, it is just distributing free Bitcoin and is earning a revenue like many sites do with ads.
You can mine some altcoins however with your browser which would, I guess, qualify as "web mining". You can check out
https://coin-hive.com/ for that. They provide a java script implementation of Monero mining algorithm.