Interesting indeed. Will it be possible to mine on more than one CPU core? Chrome is much, much faster than Firefox btw.
Also you should make it clear on the website that the mined coins are worthless as the network is still in the Testnet phase.
Well it's mentioned if you look below the connect to network.
Disclaimer
You are connecting to the Nimiq Beta Testnet. Testnet Mining does not create permanent Nimiqs.
The Testnet and your Nimiq balance may be reset at any time until the release of the Nimiq Mainnet.
Note that mining on mobile devices drains your battery.