SAN FRANCISCO (AP) -- Google Inc.'s third-quarter earnings report will provide insights into how well online advertising is holding up amid recent signs that the economy may be limping toward another recession. The report is due out after the stock market closes Thursday.WHAT TO WATCH FOR: Revenue growth and expense control typically are the two biggest keys for investors.After a year of accelerating gains in quarterly revenue, Google is expected to show a slight slowdown for the July-September period. The average analyst forecast calls for Google's total third-quarter revenue to increase by 30 percent from a year ago. That would be slightly below the 32 percent increase in the second quarter.Google's free-spending ways are also a hot-button subject for Wall Street. Investors get worried when it appears Google is getting too loose with the money pouring into the company because it makes it even more difficult to predict its future profit margins.The concerns escalated after Google co-founder Larry Page took over as CEO in April because he has always made it clear that hitting analysts' quarterly earnings targets is a lower priority than investing in projects, people and equipment that will help the company realize its long-term goals. Page, though, has gone out of his way to assure investors that he intends to spend Google's money wisely.Investors may try to gauge Page's sincerity by looking at how many employees that Google hired during the summer. Google started the year by pledging to add at least 6,200 workers before 2012 and is already well ahead of that pace. The company, which is based in Mountain View, Calif., hired nearly 4,400 employees during the first half of the year. Page has attributed part of the rapid payroll growth to fewer employees leaving the company than management anticipated after Google raised everyone's pay by 10 percent at the beginning of the year.Google is also expected provide updates on the growth of its social networking service, Plus, which debuted in late June to counter the threat posed by the popularity of Facebook's online hangout. Page has made Plus' success a top priority, even go so far as to tie employees' bonuses to how well the service does. After starting out as an invitation-only service, Plus began accepting all comers last month. By some estimates, more than 50 million people have already signed up for Plus. That would still be a fraction of Facebook's 800 million active users.In another major move beyond its main business of Internet search and advertising, Google is trying to buy cell phone maker Motorola Mobility Inc. for $12.5 billion. Management seems unlikely to talk about the progress of the proposed acquisition during Google's earnings call because the deal is still under review by the U.S. Justice Department.WHY IT MATTERS: Google is a good way to monitor the health of electronic commerce because it runs the Internet's largest advertising network.WHAT'S EXPECTED: Analysts polled by FactSet expect earnings of $8.76 per share, excluding expenses for employee stock compensation, on revenue of $7.28 billion, after subtracting Google's ad commissions.LAST YEAR'S QUARTER: In the third quarter of 2010, Google earned $217 billion, or $6.72 per share, on revenue of $6.82 billion. Excluding stock compensation revenue, Google earned $7.64 per share on revenue of $6.09 billion, after subtracting ad commissions.