Facebook Inc., the most popular social-networking site, is updating the home page with new navigation features as it reaches 400 million users worldwide, double the number a year ago.

The company, marking its sixth anniversary, is rolling out new functions on its top and side menus. The upgrades make it easier to communicate with friends and get updates on account activity, Palo Alto, Calif.-based Facebook said on its Web site. There's also a new function to interact with applications.

Facebook, started as a networking site at Harvard University, has moved beyond students to attract mainstream Internet users worldwide. The site, which had 112 million U.S. users in December, replaced News Corp.'s MySpace last year as the country's No. 1 online social network, according to ComScore Inc. in Reston, Va.

"Facebook began six years ago today [Friday] as a product that my roommates and I built to help people around us connect easily, share information and understand one another better," Chief Executive Officer Mark Zuckerberg said in a posting on the Web site. "People around the world are using the service to share information about events big and small and to stay connected to everyone they care about."

The home page's redesign has links to content such as games and applications in a panel to the left of the screen. Each button opens to a "dashboard" presentation of recent Facebook postings, such as friends' photos, calendar events and applications. It also offers users the chance to join online games and activities.

A top-screen menu bar provides access to users' latest messages, notifications and requests.

"We hope the simplified design of the home page will make it easy for you to stay connected with the people, applications and activities that matter the most to you," Jing Chen, a Facebook engineer, said in a blog posting.

Facebook has used its growing traffic to boost sales of advertising. The company said in September that it was generating positive cash flow, reaching that point earlier than expected.