It's horrendously horrible.

Like any typist, if I make a typo, I immediately hit the backspace key, and that exits your site and brings me straight back here. So it's completely useless.

Apart from that, it's a pointless exercise. Nobody sits and types sequences of very obscure words, and it's not a useful skill. Which is why normal typing programs get you typing typical English (or whatever) sentences.

Sorry if this sounds harsh. I can't imagine why you did the program that way, but I'm willing to listen to reason ;-)

Nice. You need to start the counter once the first letter is typed.

It measures a skill very different from ordinary typing, so, no.