A good excerpt from Yahoo Finance:
The main rule for selling is to sell what you see, not what you think. This rather difficult concept is counterintuitive, because stocks often climax and fall off the cliff even while their fundamentals, earnings history and future look spectacular. Chipmaker Marvell Technology Group (NASDAQ:MRVL) breezed past Thomson First Call consensus estimates in each of the past 13 quarters, by 2% to 11%. Earnings bounded 50% or more and sales 31% and higher in the past eight quarters. Double-digit earnings and sales growth are expected through next year. Profit margins have also been strong, while cash flow has been growing. So why is the stock 52% below its all-time high?
You don’t need to know why it is 52% off its all-time high. You just need to know that it is.