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 online broker optionsXpress (Nasdaq: OXPS) shed as much as 10% in early trading today on heavy volume.

So what: Confusion reigned supreme this morning for optionsXpress shareholders. The company is getting ready to pay out a hefty $4.50 dividend to its shareholders, and the record date for the dividend was yesterday. Which explains today's drop, right? Well, it does and it doesn't. Though investors can normally expect to cash in on a dividend as long as they are holding as of the record date, the Nasdaq exchange has a rule that if the payout is 25% or more of the stock's value, then shareholders have to hang on to the ex-dividend date, which is Dec. 28.

Now what: Investors who knew better this morning may have gotten to swoop in and grab some quick gains on optionsXpress shares. Shares may continue to recover losses from this morning and then stagnate a bit ahead of the ex-dividend date.

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Nasdaq OMX Group is a Motley Fool Inside Value recommendation. optionsXpress Holdings is a Motley Fool Stock Advisor selection. Motley Fool Options has recommended writing covered calls on Nasdaq OMX Group. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Fool contributor Matt Koppenheffer owns shares of optionsXpress, but does not own shares of any of the other companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy assures you no Wookiees were harmed in the making of this article.