"Would the knowledge to count cards do me any good in an online game?"

It would, with the following assumptions:

A. That the decks used in the software program are complete. If the program uses short decks, the disadvantage is almost certainly unsurmountable. B. That the ordering and the dealing of the cards is random. In other words, we assume that the program doesn't make sure that the house wins at a specific rate no matter what. C. That the decks are not shuffled after every round. Otherwise, you're playing against a virtual CSM, which is hopeless for a straight counter. D. That you are getting decent penetration and good rules to fight against. Otherwise, you are better off spending time elsewhere.

These are some pretty tough assumptions, you will admit! No right-thinking casino owner, even a web casino owner, would allow excessive vulnerabity in his game, especially to every casual card counter and his cousin. Why should he?

There are ways, of course, to beat online Blackjack and they do not involve (just) counting -- but that's not what you're asking now, is it? (The starting point in the quest for the gold starts with the freebies. Shop around.)

"Also what is a good money management system for playing online?"

If you're talking about progression-based systems, read no further. But you certainly came to the right place to ask!

If, on the other hand, you refer to legitimate betting strategies, well, the same money management rules that apply in "real-life" 21 apply in the online game. The principles of Risk of Ruin and correct betting strategies do not change because the table is made of bytes! The difference with "real-life" BJ is that you can drop all the camouflage. Dress in your underwear, have all the BJ books nearby if you wanna, pick your nose and swear at the dealer till you're blue in the face. You'll be still welcome at the joint!

But, on a more serious note, most online casinos now monitor the players' play and will sometimes identify (and bar) dangerous players, aka winning players.

--Cyrus