Zillow Inc., a real-estate information website, said it plans to sell 3.18 million shares of its Class A common stock in a secondary public offering.

The company will use the proceeds of the sale for general corporate purposes. Some of the proceeds may be used for acquisitions or investments, though the company has no current agreements or commitments, Seattle-based Zillow said Wednesday in a statement.

Citigroup Inc. will be lead bookrunning manager of the offering, with Goldman Sachs Group Inc. as joint bookrunning manager. An additional 325,000 shares will be sold by some existing shareholders, according to the statement.

Zillow’s website allows home buyers, sellers, renters and managers to list and search for properties, home-price estimates and other information.

The company’s shares slipped 3.5 percent to $40.99 in extended trading following the announcement. Earlier, they had gained 2.3 percent to $42.43 at the close in New York. The stock has more than doubled since Zillow sold shares at $20 apiece in an initial public offering in July 2011.