Why Google got slammed for its earnings

Google shares are tanking, and it's not because the company's third-quarter results hit early.

Sure, that's a pretty big no-no, but what's really upsetting investors is the numbers themselves. Results were pretty lackluster across the board, and Motorola can't be blamed for all of it.

Here's what's spooking investors:

The stock has been on a tear
First of all, keep in mind that Google's stock has been on a tear as of late, rising more than 30 percent this summer before hitting a record $774.38 earlier this month. That prompted a host of analysts to raise their price targets for the stock, including Citi's Mark Mahaney, who issued a bullish report saying the stock could hit $850. After results came out today, the stock tumbled 9 percent before being halted. It recently was down about 8 percent at $694.09.

Results came in well below expectations
Google's overall results -- combining its core operations and its Motorola Mobility acquisition -- came in a little light. That includes revenue and adjusted per-share earnings, according to Thomson Reuters, and that's something the Street never likes to see.

Google's core operations are partly to blame
It would be easy to blame all of that on Motorola, which clearly has had more than its share of troubles, but Google's core business wasn't exactly humming either.

The company's advertising cost-per-click dropped 15 percent year-over-year. Essentially, that measures the average amount advertisers paid Google for each time someone clicked on an ad. A 15 percent decline is pretty steep and is worse than analysts were expecting.

BGC Partners analyst Colin Gillis told CNET that expectations were for a 6 percent to 7 percent drop, and this slide is the fourth consecutive decline. The reason cost-per-click is falling is because more clicks are coming from mobile devices, and Google makes less for those clicks.

Along with that, Google's growth in paid clicks, or the number of times users clicked on search ads, decelerated, rising only 33 percent. The second-quarter's click growth jumped 42 percent, and that even included a tougher comparison in the year-ago period, Citi's Mahaney noted.

In addition, Google's traffic acquisition costs, the amount it has to pay its affiliates, rose 25 percent this year, weighing on how much revenue it can actually generate from its core search business.

Then there's Motorola
And then we get to Motorola. While the business is in full turnaround mode, the handset maker's struggles never seem to end.

Today, Google reported revenue from Motorola that fell short of analysts' expectations, and that's for both the mobile and cable box businesses.

Add to that a pretty big operating loss of $151 million, and you have some pretty unhappy investors.

"Motorola is a total expense millstone," BGC's Gillis said.

Google likely has a bit of explaining to do during its conference call with analysts. Stay tuned for CNET's live blog of Google's earnings later today.