This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
Indicates whether or not the social media provider's content sidebar is currently visible.
var visible = navigator.MozSocial.isVisible
true if the sidebar is currently visible; otherwise it's
Not part of any specification.