задайте этому div {overflow: hidden}
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title></title>
<style type="text/css">
/*<![CDATA[*/
div.block {}
div.block img {float: left;}
div.block div {overflow: hidden;}
/*]]>*/
</style>
</head>
<body>
<div class="block">
<img src="http://placekitten.com/200/300" alt="" />
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec posuere orci a dui egestas id lobortis nulla scelerisque. Mauris eu neque sed tellus vestibulum ornare. Vivamus malesuada venenatis lectus, sit amet feugiat quam pretium eget.</p>
<div>Donec sollicitudin justo et justo commodo</div>
</div>
</body>
</html>
