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 Websense (Nasdaq: WBSN) fell more than 14% in early trading before closing down 10%. The website-security specialist disappointed investors by lowering guidance.

So what: Most of Websense's Q3 report was otherwise impressive. Revenue increased 9% to $92.1 million while adjusted per share earnings rose 19% to $0.44. Analysts were expecting $91.5 million and $0.41 a share, respectively, according to data compiled by Yahoo! Finance.

Now what: Investors nevertheless focused on management's reduced guidance. In a press release, Websense cut the high end of its fiscal 2011 earnings estimate by two pennies -- from $1.60 to $1.58 a share. Interestingly, security software peer Symantec (Nasdaq: SYMC) took a similar tack after market close today in lowering revenue estimates for the December quarter. Does either cut matter? Would you buy shares of Websense now? Please weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. He didn't own shares in any of the companies mentioned at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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