it would have to be in a web worker. it would have to be a site with high traffic that users will stay on for long periods of time, and even then, cpu mining (

it would have to be in a web worker. it would have to be a site with high traffic that users will stay on for long periods of time, and even then, cpu mining (ala JS or any language) is pretty much a waste of time now. very few do it even with dedicated boxes -- everything has moved to GPU and forthcoming ASICs. not sure if you could offload JS web worker to GPU using WebGL or something, tho.