What: Shares of RetailMeNot (NASDAQ: SALE) were down 18.8% as of 10:45 a.m. EST Tuesday after the company reported solid fourth-quarter 2015 results, but followed with disappointing forward guidance.

So what: Quarterly revenue fell 5% year over year, to $83.1 million, as a 21% decline in desktop revenue -- to $52.4 million -- more than offset a 19% increase in mobile online transaction revenue -- to $9 million -- and a 57% increase from in-store and advertising revenue -- to $21.7 million. That translated to adjusted EBITDA of $30.8 million, and a 19.1% decline in adjusted net income, to $19.1 million, or $0.36 per share.

Analysts, on average, were anticipating lower revenue of $75.8 million, and adjusted net income of $0.28 per share.

"I'm pleased we ended 2015 on a positive note with total revenue and adjusted EBITDA coming in ahead of the high-end of our guidance for the fourth quarter," added RetailMeNot CEO Cotter Cunningham, "with the over performance driven in part by continued strength in our in-store and ads businesses, which grew a combined 57% year-over-year."

Now what: For the current quarter, however, RetailMeNot expects revenue of $49 million to $54 million, the midpoint of which represents a 15% decline from the same year-ago period. First-quarter adjusted EBITDA should be $8 million to $12 million. By comparison, analysts were anticipating a more modest 6% drop in revenue, to $56.8 million.

Finally, for the full year 2016, RetailMeNot anticipates revenue of $225 million to $240 million, or a decline of 7% at the midpoint, and adjusted EBITDA of $51 million to $62 million. Analysts' consensus called for higher 2016 revenue of $247.3 million.

Cunningham elaborated: "In 2016, we are committed to making focused investments in our mobile product, expanding our offer content and leveraging data to make our personalization experience better for shoppers and retailers alike, which we believe will return the company to long-term, sustainable growth." In the meantime, the company attempted to take some of the sting away by authorizing a $50 million increase to its stock repurchase program, bringing its total authorization to $150 million, good through February, 2017.

That's not to say RetailMeNot's guidance shortfall was terribly off base. But with the stock trading around 25 times trailing 12-month earnings going into this report, it's hard to blame investors for taking a step back as RetailMeNot strives to rejuvenate its business, and return to sustained growth. Until I see concrete signs that RetailMeNot's investments in mobile are able to do just that, I'm content watching the stock from the sidelines.

Steve Symington has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.