You can know when someone is online on Facebook without downloading any software. We can’t stay online all the time to chat with our friends on Facebook. And also we cannot miss our favorite friends. So what can we do? I think there is some software for PC/Android that notifies you when friends go online. The problem is that we can’t leave our computer on all the time. And the phone’s app is going to eat up the entire phone’s battery. Now what? That’s where my crazy little idea comes into play! Facebook has a notification system that notifies you about your friend’s activities. Facebook notifies you when a friend likes/comments/shares your posts. You can exploit this. I mean use it for this purpose. You have to turn on notifications by SMS on Facebook. When adding the phone number for the first time you will have to verify it. After you enable notifications you will start receiving notifications by SMS. It may become a headache if you have so many friends. You can customize notificat...