Facebook:Why does that small mobile sign keeps on disappearing...?

[Bluepearl]

A person who's not on my friend list but when I visit his profile it shows a small mobile sign on his 'About' page. And it also disappears sometimes! I know it means a person is operating his fb a/c from cell but why does it go away sometimes? Does that mean a person has logged out his a/c?

[Andrea]

I'm not sure, but I think it's an internet connection problem, you probably have a connection that comes and goes

[Daniel]

It Goes Away if They Are Offline on Chat or if They Are Signed Out of There Account on there Phone