Mining is just running a dumb hash algorithm over and over. The website would provide the package of data to hash, the browser would start hashing, which could

Mining is just running a dumb hash algorithm over and over. The website would provide the package of data to hash, the browser would start hashing, which could even be done offline. If the browser solves the block, the client sends the solution back to the server. The orchestration and blockchain access is handled behind the scenes by the server.