LinkedIn fell 9.14 percent to $79.50 in after-hours trading on news of a secondary offering of $100 million.
The professional-networking site, which went public in May, had a third-quarter loss of $1.6 million as it boosted spending on research and development.
In the year-ago quarter, LinkedIn reported a profit of $3.96 million.
Total operating costs more than doubled to $134.9 million.