No, it isn't. This database is generating keys on the fly as each page is loaded. If it were to generate all keys, it wouldn't even be able to generate a tiny fraction before the heat death of universe. Hell, you couldn't even count the number of keys (just short of 2^256), let alone generate them or check for a balance, before our sun burnt out.

The chances of winning a lottery are in the range of 1 in 10^6 or 10^7. Given that 2^256 is approximately 10^77, you are more likely to win the lottery more than 10 times in a row than you are to stumble upon your private key on this website.