The forex market is an over the counter market. This means there is no centralized exchange that you are trading through. Therefore the regulation your broker has to abide by is very important. Size is also important to make sure they don’t go belly up and take your money with them.

If you’re new to trading, then the micro account is a good way to get started since you can begin with a smaller balance to test things. But again, check on the regulation of the broker.

The most reputable countries and their regulators are the FSA in the United Kingdom, the SFC in Hong Kong, the CFTC and NFA in the United States and ASIC in Australia.

http://www.cftc.gov/opa/enf98/opaforexa15.htm

Also, just to add to an earlier poster’s very good point about "retail forex" trading:

Very few retail traders can open a "real" forex account that can trade against bank trading desks. Probably need $2,000,000 minimum or so to do that, plus be able to convince them that you’re something big.

The "forex" accounts typically promoted on the Internet aren’t the same — with those, you’re actually trading against your own broker, who issues OTC securities to you. This puts you in the rather awkward position of being in diametric financial opposition to your broker. Guess what typically happens to such accounts, over time?

The Chicago Mercantile Exchange (CME) allows trading in currency futures. This is a real, open market. The downside is that it requires a lot more capital than "retail forex" (probably 20K minimum), and these are futures, so that adds a little complexity to things, for the uninitiated. And you will still likely lose all your money, quickly, anyway, unless you’ve got some real advantage over the market, or you just get really lucky. If I really wanted to learn about what moves forex markets, I’d start by heading to my local university library and browsing the Journal of Finance and similar publications; and even then, there’s no guarantees.