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.