Basically, you want to add a “hideme” class to every element you want hidden (then you set that class to “opacity:0”;
Then, using jQuery you set a $(window).scroll() event to check the location of the bottom of every “hideme” element against the bottom edge of your visible window.
Here’s the meat of it …
/* Every time the window is scrolled ... */
$(window).scroll( function(){
/* Check the location of each desired element */
$('.hideme').each( function(i){
var bottom_of_object = $(this).offset().top + $(this).outerHeight();
var bottom_of_window = $(window).scrollTop() + $(window).height();
/* If the object is completely visible in the window, fade it in */
if( bottom_of_window > bottom_of_object ){
$(this).animate({'opacity':'1'},500);
}
});
});
Here’s a full jsfiddle: http://jsfiddle.net/tcloninger/e5qaD/