Allready Answered here -->> Dynamic Scroll Position in Jquery
There is a great plugin to do this called WAYPOINT
I have setup an example on jsfiddle check it out
HTML
<div class="first"></div>
<div class="second"></div>
CSS
.first {
background:green;
height: 600px;
width:100%;
}
.second {
background:red;
height: 600px;
width:100%;
}
JS
$('.second').waypoint(function() {
alert('You have scrolled to an entry.');
}, {
offset: '100%'
});