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

This afternoon, the Dow Jones Industrial Average (DJINDICES:^DJI) closed the day up 21 points, or 0.14%, and now sits at 15,783 and set once again a new all-time closing high. The move comes despite none of the index's 30 components reporting earnings today and very limited economic data being released. Additionally, only 13 of the Dow's 30 components ended the trading day in the green, but thanks to a big move by IBM, the index posted a gain for the session. So since the majority of the blue-chip stocks lost value today, let's take a look at the top three losers of the session.

Shares of Boeing (NYSE:BA) lost 0.72% of their value, making it the Dow's worst-performing stock of the session. The move comes after Japan Airlines reported that one of its 787 Dreamliners had a battery problem during a flight on Friday from Helsinki to Tokyo. The airline reported that while the battery was not smoking or showing any signs of overheating, cockpit indicators did show there was an issue. The battery has been removed from the plane and inspectors are looking into the issue at this time. While nothing serious happened, this was just another reminder to investors that owning Boeing shares still carries some risk, despite the fact that the stock is up more than 75% year to date and has been the best-performing Dow component of 2013.  

The second-biggest loser within the Dow today was Microsoft (NASDAQ:MSFT), which lost 0.5%. After today's drop, the stock is down more than 1.5% since jumping 4.2% and hitting $38.18 last week on news that the company had its shortlist of candidates to replace retiring CEO Steve Ballmer. The stock price jump last week on that news was a little irrational and the pullback since then is simply the market repricing the stock and should not be seen as a negative event. Furthermore, the company has a lot going on and it should be an exciting time for investors in the coming months with the release of the Xbox One unit, an announcement of a new CEO, and the merger of the Nokia acquisition, to name a few. While these events will be fun to see play out, shareholders need to remain focused on the long-term goal and not get overly concerned with large declines if the different transitions or product launches don't go as planned.

And lastly, the third-worst Dow performer of the session was Verizon (NYSE:VZ), which lost 0.48%. Some investors have begun to question what the future of Verizon and AT&T may look like since the U.S. telecom industry's growth is now beginning to slow and it seems clear the top two players are struggling to find new growth avenues. A perfect example of this is Verizon's recent purchase of Vodafone's 45% stake in the Verizon Wireless joint venture. Or the reports that Verizon would be moving into Canada by purchasing a smaller player within that market. We have even seen reports, though unconfirmed, that AT&T may buy Vodafone or another wireless operator in Europe. Fears about slowing growth may be causing investors to find greener pastures.

Fool contributor Matt Thalman owns shares of Microsoft. Check back Monday through Friday as Matt explains what causing the big market movers of the day and every Saturday for a weekly recap. Follow Matt on Twitter @mthalman5513

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