2 строчки jquery кода всего...
<!DOCTYPE html>
<html lang="en">
<head>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
.wrapper{
width: 960px;
margin: 0 auto;
}
.sidebar{
width: 200px;
height: 400px;
background: grey;
float: left;
}
.container{
width: 760px;
height: auto;
float: left;
background: red;
}
</style>
<script>
$(document).ready(function(){
var hidesize = $('.sidebar').attr('height');
$('.container').text("Высота блока:" + hidesize);
});
</script>
</head>
<body>
<div class="wrapper">
<div class="sidebar">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Eos ut ea beatae, facere optio? Repellat cumque illum amet illo nostrum ex iusto dignissimos, sed, culpa id deserunt voluptatum, expedita quis.</div>
<div class="container">
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo ducimus animi pariatur praesentium, modi accusantium vero dolore. Illum voluptas, harum illo ducimus sequi modi dolore perferendis, adipisci laudantium corporis voluptate!
</div>
</div>
</body>
</html>