class method Element.visible
Element.visible(element) → Boolean
      Tells whether element is visible (i.e., whether its inline display
CSS property is set to none.
Examples
<div id="visible"></div>
<div id="hidden" style="display: none;"></div>
And the associated JavaScript:
$('visible').visible();
// -> true
 $('hidden').visible();
// -> false
Notes
Styles applied via a CSS stylesheet are not taken into consideration. Note that this is not a Prototype limitation, it is a CSS limitation.
<style>
  #hidden-by-css {
    display: none;
  }
</style>
 [...]
 <div id="hidden-by-css"></div>
And the associated JavaScript:
$('hidden-by-css').visible();
// -> true
      
      
        This method can be called either as an instance method or as a generic method. If calling as a generic, pass the instance in as the first argument.