That's one of the inherent features of facebook and some others like viber.. <br />
Some social networks/ chat engines allow you to choose whether to show that or not.. <br />
Sadly I don't think Facebook does it.. <br />
I may not look it but I am a geek.. :P
There is no way to do that. You can only do that with an extension on your browser on an actual computer. It sucks.
You think that's bad, you should try this site called Experienceproject....
Check your settings.