You're really just wasting electricity. Even if your computer was able to search a thousand or a million times faster, the chances of ever finding a match within your lifetime are effectively zero. You'd have more chance of winning a (real world) lottery.

Is it possible to find addresses with balances or (more likely) which have had balances in the past? Yes: look up SHA256 brain wallets, broken key generator code, deliberately weak keys, user mistakes, etc.

Can you find them by generating random keys via a website? No. (The code I posted above generates random keys - it was meant to be a joke. )