How can a company report a big fat loss and then see its stock go up? And how is it that some companies' shares fall, even though they generate a profit?

It's all about "expectations." If a company's results miss expectations, the stock will usually fall; if the results meet or exceed expectations, the stock will usually rise.

But whose expectations are we talking about here?

That's right -- investors, specifically analysts at the big investment houses, who pore over the company's filings and news releases and come up with their projection of how the company has performed over the quarter.

No company likes to see its stock go into a tailspin, especially at earnings time, so companies do everything they can to avoid missing expectations. The biggest weapon in their arsenal is something called "guidance;" also known as "managing expectations."

Guidance is when the company calls up investors ahead of the earnings release and says "Hey chaps, we've had a few problems recently. It looks as though our numbers aren't going to be so good this quarter."

The analysts factor that into their calculations, and their expectations are lowered. That way, if the company's results are terrible, no one is surprised. And if the results are really good, then the stock gets a bump.If this sounds like manipulation, well, maybe it is.