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.

Stocks regained a bit of their lost luster today as markets once again got a boost from a high-profile individual investor. After falling early in the session on continued worries about how long the bull market can last without a substantial correction, stocks managed to rebound by the early afternoon, and then well-known activist investor Carl Icahn's announcement that he had taken a substantial position in Apple helped send the tech side of the stock market even higher. At the close, the Dow Jones Industrials (DJINDICES:^DJI) finished up 30 points, with the Nasdaq Composite (NASDAQINDEX:^IXIC) climbing 0.4% due largely to Apple's contribution.

Yet several stocks missed out on the Dow rebound. Microsoft (NASDAQ:MSFT) was the Dow's biggest decliner, falling almost 2% after an analyst downgrade. Stifel Nicolaus said that the best way for the company to unlock shareholder value would be to break itself up into two separate businesses, with one focusing more on business and tech infrastructure plays, while the other takes products like the Xbox and tablet segments as well as the Windows operating system. That's a theme that others have echoed, but Microsoft seems to have no plans to follow through on the suggestion, which hasn't helped the stock.

Alcoa (NYSE:AA) was also under pressure, shedding 1.3%. After a very nice run-up of more than 6% in the previous three trading sessions, the aluminum giant's stock was probably overdue to give back some of those gains. Positive news from China had the stock on the rise late last week, but the prospect for Federal Reserve tapering in the U.S. offset some of the enthusiasm investors were feeling. The tug-of-war between developed and emerging markets might well last for a while, and the winner could determine Alcoa's eventual fate.

Finally, Verizon (NYSE:VZ) dropped 1%. A big jump in bond yields was likely behind the slide, as high-dividend telecom companies have tended to trade somewhat in unison with the bond market. Until Verizon establishes where its growth will come from, many investors treat it merely as an income-oriented stock, and that leaves its shares vulnerable to interest rate oscillations. If the company can find new growth avenues -- whether in its recent Canadian expansion plans or through a complete takeover of its Verizon Wireless joint venture -- then it could prove icing on the cake for many investors.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool owns shares of Microsoft. 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.