What is the best daytrading software that's free online?

One of the best stock market packages has to be WALL STREET ANALYSER.
Because it has everything you need to trade the stock market on a daily,
weekly or monthly timeframe. You update the stock and index database,
with the most recent prices from yahoo finance, next you can pull up a
chart of that stock or index and overlay moving averages or any indicator
you can think up.

There are TWO outstanding features of wall street analyser which are the ability
to design your own INDICATORS and a great BACKTESTING section.
Being able to design your own indicators means you can really stay ahead of the
curve in trading by using non standard indicators that most traders will not
be using, this gives you a great advantage over the competition. The Backtesting
facility can include your own indicators as well and you can backtest all stocks
or just one. Once you have played around with the backtesting facility a bit, you
will soon notice that some indicators work fantastic on some stocks but lousy on others.

This shows that every stock or index has it's own personality and you have to
match the particular set of indicators to a stock. One size does not fit all
with the markets.

That is one of the reasons why changing systems every month after a few losses is
not the way to trade. You have to trade like a casino who have only a small
advantage over the average punter, which is about 2.5%. But when played long
enough ie 24/7 pulls in millions for the casinos. It's exactly the same in trading,
you need an edge of between 2-5% only to make millions if you trade long enough.

That is why it's so important to keep your losses to a minimum because the
BIG LOSERS really wipe you out.