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 Focus Media Holding (Nasdaq: FMCN) jumped 10% in intraday trading early today on very little news -- so what's going on?

So what: It appears investors who may have been scared away from China MediaExpress (Nasdaq: CCME) are putting their money into competitors today, considering the price action. China MediaExpress is down, but both Focus Media and VisionChina are moving higher in trading today.

Now what: Yesterday, Citron Research questioned China MediaExpress's business, and the tug-of-war continued today when management responded with a statement that basically said "rubbish." All we know for sure today is that China MediaExpress is down and Focus Media is up, indicating a shift of sentiment in the stocks. I don't see the move today as a reason to change your investment thesis on any of these companies, but I do recommend doing lots of homework before putting hard-earned dollars into any of them. They can all pop or plunge at a moment's notice, and I'm sure we'll be back very soon to tell you why they made another move.

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

Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

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. The Motley Fool has a disclosure policy.