Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of broadband systems builder Calix (NYSE: CALX) opened today's trading 19.6% below Friday's closing price, though the stock recovered to a much smaller fall very quickly on rather average trading volume.

So what: Let's cut to the chase: There's nothing wrong with Calix today, and that bottom-scraping quote comes from one trade of a measly 328 shares. Some poor trader, probably an individual investor like you or me, placed a market order to sell at the worst possible time, conversely making a buyer very happy.

Now what: Calix is a very thinly traded stock, which opens the door to exactly this type of mishap. The reverse scenario played out for General Cable a few months ago, for example. Use market orders at your own risk, dear Fool.

Interested in more info on Calix? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.