To track an iPhone online, the iPhone's Find My iPhone feature must be on, and it must have Internet access. Navigate to the iCloud website and log in as the owner of the iPhone. Click the Find iPhone option and the location of the phone appears on a map.
To track an Android phone online, the phone needs to connect to a Google account, and it must have Internet access. In addition, the owner must enable the feature that allows the Android Device Manager to locate the phone. Navigate to the Android Device Manager website, and log in with the same Google account as the phone to track the location of the phone.