One rule that we learned from the Internet boom is just because a company appears to be doing well, does not mean that it actually is. One such example of this would have to be Amazon.com. At one time, there was speculation they would shrivel up with the tech bubble of the ’90s. Yet today, they are still around and kicking.

Only one problem. Even with their revenue rising, they still are not making the kind of profits that the industry would like to see from them.

Online retailer Amazon.com Inc. on Wednesday reported a 31 percent jump in revenues in the fourth quarter, but it’s profits failed to meet Wall Street expectations and its stock fell by more than 13 percent in after-hours trading.

The Seattle company said net income for the quarter ended Dec. 31 was $347 million, or 82 cents a share, compared with profits of $73 million, or 17 cents a share, for the same period a year ago. Net income for the latest quarter, however, included a $244 million tax benefit.

Excluding the tax benefit, profits were $149 million, or 35 cents a share, which fell below analysts’ average estimate of 40 cents a share, according to Thomson First Call. Amazon.com’s stock fell 13.68 percent, or $5.73, in after-hours trading to $36.15.

Revenues for the quarter rose to $2.54 billion from $1.95 billion a year ago.

In the last couple of years, Amazon.com has come under increasing pressure from major brick-and-mortar retailers, such as Wal-Mart Stores Inc., who are increasingly leveraging the web to boost sales. To counter the tougher competition, Amazon.com has offered promotions, such as free shipping on orders over $25, which have cut into profits and have worried some analysts.