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 industrial cleaning specialist Tennant (NYSE: TNC) were taken to the cleaners by investors as shares fell as much as 17% in intraday trading after the company reported third-quarter results.

So what: The current-quarter results for Tennant actually looked pretty decent. Sales were up 11% year over year to $187 million, which basically matched analysts' estimates. Earnings per share fell short of expectations by $0.01, but the $0.50 that the company earned was 28% better than last year.

While the slight earnings miss wasn't good news for investors, the company's outlook for the fourth quarter may have been the more worrisome reveal. Thanks to recent economic concerns, Tennant lowered the low end of its revenue and earnings outlooks for the year. The respective midpoints are now at $755 million and $1.93. On average, Wall Street analysts were looking for $1.99 in per-share profit on $761 million in revenue for the year.

Now what: Even if Tennant hits the now-lower midpoints, its 2011 revenue and earnings would still show solid growth over 2010. Broadly, this is a pretty boring, but necessary business that many investors may overlook -- the type of company I'd normally like to own. However -- even though my fellow Fools at Motley Fool Stock Advisor are currently big fans -- like many other small- and mid-cap stocks, Tennant's stock's valuation just doesn't look all that attractive to me right now.

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