NEW YORK (AP) — Select Comfort shares tumbled to a 17-month low Monday after the company warned that sales were weak in February, and it will likely fall short of its own goals for the current quarter.

THE SPARK: The Minneapolis-based company blamed the sales shortfall on changes it's made to its advertising strategy. It said that it's correcting its marketing plans.

THE BIG PICTURE: Select Comfort makes Sleep Number-brand mattresses, as well as pillows and sheets. Mattress makers overall have been struggling with intense competition in recent months as they battle to get consumers to make big-ticket purchases.

Since announcing lower-than-expected fourth-quarter results and a weak 2013 guidance in January, the company's stock has lost about 25 percent of its value.

Select Comfort said it will discuss its outlook for the rest of the year after it releases first-quarter results on April 17. The company does not provide quarterly financial guidance.

THE SHARES: Down $3.32, or 16 percent, to $17.20 after dropping as low as $16.62 earlier Monday. That was the stock's lowest price since October 2011.

Shares had traded from $19 to $35.60 in the past 12 months.