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.scrolldown {
	background: url("img/icons.png") no-repeat scroll -13px -162px transparent;
	width: 59px;
	height: 31px;
	display: block;
	position: absolute;
	bottom: 20px;
	left: 50%;
	margin-left: -30px;
	cursor: pointer;
}

/* Scroll Down Button */

$('.scrolldown').click(function(){
    $('html, body').animate({ scrollTop: $(this).parent().innerHeight() - 94}, 600);
    return false;
});

<span class="scrolldown"></span>