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 Vistaprint (Nasdaq: VPRT) have dropped today by as much as 12% after an analyst downgraded the stock.

So what: Barclays cut its rating on Vistaprint from "equalweight" to "underweight," which is analogous to a "sell" recommendation. The firm also reduced its price target from $35 to $29, and shares have nearly fulfilled that prophecy today alone with the low trade of $29.06.

Now what: Analyst Mark May cited "intra-quarter data checks, recent exchange rate changes and valuation analysis" for concern that Vistaprint may miss the Street's estimates for fourth-quarter results and fiscal-2013 guidance. Barclays reduced its earnings estimate to a range of $1.72-$1.73 per share in 2012 and $1.79-$1.80 in 2013. The rest of the Street is perched on earnings per share of $1.78 this year and $2.05 next year.

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