Александр83,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
body{
position: relative;
}
.aaa{
position: absolute;
background-color: #FFFF00;
min-width: 338px;
height: 348px;
border: 1px solid #2992d9;
border-radius: 3px;
margin-left: 5px;
display: block;
top: 0px;
z-index: 999;
}
.bbb{
position: relative;
background-color: #f9f9f9;
border: 1px solid #e5e5e5;
margin-left: 245px;
width: 350px;
height: 1588.5px;
z-index: 998;
}
p{
height: 1000px;
background-color: #A9A9A9;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script src="https://abouolia.github.io/sticky-sidebar/js/sticky-sidebar.js"></script>
<script>
$(function() {
var a = new StickySidebar('.bbb', {
topSpacing: 20,
bottomSpacing: 20,
containerSelector: '.bbb',
innerWrapperSelector: '.aaa'
});
});
</script>
</head>
<body>
<p></p>
<div class="bbb">
<div class="aaa">плавающий банер</div>
</div>
<p></p>
</body>
</html>