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  Lexmark International Inc (NYSE:LXK) fell more than 12% on Tuesday after the company turned in solid first-quarter results, but weaker-than-expected forward earnings guidance.

So what: Adjusted quarterly revenue fell slightly year-over-year to $881 million, easily exceeding expectations for first quarter sales of $855.78 million. Lexmark also pointed out that, excluding planned and ongoing declines in Inkjet Exit revenue, sales would have grown 6%. This translated to adjusted earnings of $0.92 per share, which also beat analysts' estimates calling for earnings on the same basis of just $0.87 per share.

However, Lexmark also called for total revenue in the current quarter to decline 2% to 4% from last year, which should result in adjusted earnings of $0.85 per share to $0.95 per share. Analysts, on average, were looking for second-quarter earnings of $0.94 per share on revenue of $856.08 million.

Now what: Lexmark continues to buy back shares and pay dividends to reward investors for their patience as it works to drive better margins going forward, but I'm not particularly interested in buying today. Shares might look cheap trading around 10 times last year's earnings, but I can't blame investors for taking a step back today given the stubborn, gradual declines in Lexmark's top line. Despite today's drop, I'm perfectly happy remaining on the sidelines.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.