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 Aeropostale (NASDAQOTH:AROPQ) finished down 10% Friday after the teen-focused clothing retailer posted a weak quarterly earnings report.

So what: Aeropostale reported a per-share loss of $0.16 during the seasonally slow quarter, a penny better than analysts had predicted. Perhaps more concerning, overall revenue fell 9%, though that also topped analyst projections, and same-store sales tumbled 14%. The company blamed clearance markdowns from the holiday season for the revenue drop and also said colder-than-normal weather kept shoppers away. Guidance for the current quarter was lower than expected at a loss of $0.20-$0.15, versus a consensus of a loss of $0.06, indicating that the turnaround plan is not going as hoped.

Now what: The teen clothing market is notoriously fickle, and brand loyalty can change in a flash. A 14% drop in comparable sales would normally be alarming, but I'd wait to see the full year's results before assuming that pattern will hold. Rival Abercrombie & Fitch shares were off 8% after a similarly dismal quarter, so this may have just been a result of industrywide pressures. To stay up to date on the latest Aeropostale news, add the company to your Watchlist here.