Facebook (www.facebook.com) is the world's most popular social networking service. Its membership was nearing 500 million in 2010, and half of those members visit the site every day. People use Facebook to keep up with friends and family, to reconnect with classmates, and to promote their careers and businesses. Companies use Facebook to network with customers, and nonprofits use it to connect with supporters. It's simple to join Facebook, but navigating its features can be confusing at first. Here's what you need to know to get the most from your Facebook experience.