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.

2014 hasn't been kind to the stock market so far, and Monday's performance added to the modest losses that major-market benchmarks have suffered in the first three trading sessions of the New Year. Yet while drops among the major indexes were limited to 0.25% to 0.5%, Select Comfort (NASDAQ:SCSS), First Solar (NASDAQ:FSLR), and Ruby Tuesday (NYSE:RT) fell much more dramatically today.

Select Comfort plunged 19% after it issued a revenue warning for its holiday quarter. The mattress and bed specialist says it expects sales for the quarter to rise just 5%, well off the double-digit percentage growth it initially projected. Investors therefore braced for correspondingly lower earnings, although Select Comfort didn't pin down a figure on the net-income front. With competitor Tempur Sealy (NYSE:TPX) having taken advantage of consumer interest at the lower end of the mattress segment, Select Comfort might be suffering from a lack of premium demand for its Sleep Number systems.

First Solar fell almost 10% on a downgrade from Goldman Sachs, which issued a rare sell rating on the solar company. Goldman believes that First Solar's utility-project focus will end up being its undoing, as residential-solar stocks have gotten a lot more attention and appear to have more immediate growth potential. Nevertheless, First Solar could still produce solid growth as long as prices keep coming down and its operational strength in putting together utility-scale projects continues to outpace its competitors.

Ruby Tuesday dropped 9% in advance of its earnings report due out Wednesday after the market closes. The ailing restaurant chain has working hard to restructure and reduce its debt, making smart repurchases to try to cut its interest costs. It's also made changes to its menu and closed some of its stores in an effort to reduce massive declines in sales at its existing locations. Judging from today's performance, investors are bracing themselves for more of the same despite Ruby Tuesday's best efforts to turn things around.

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Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter: @DanCaplinger. The Motley Fool owns shares of Tempur Sealy International. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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.