hi i want to know that how to set mobile icon on facebook chat just like a saw may friend they are online ?

[Brittany]

Not entirely sure what your question is..
But as long as you're logged into Facebook from the application available for whatever smartphone you have, it will automatically appear.
Or at least it does for me.
In terms of what phone you should buy, Don't buy a phone just to use an application. That's just stupid, Look into other positives in a phone,
As for would it work on a Nokia Lumia 520, well I have no idea what phone that is, and I'm to lazy to google but if it's a smartphone it should have some sort of app store, and if it does, you should be able to find the Facebook application no problem.