Image goes beyond container div bounds

.intro {
margin: 10px;
outline: 1px solid #CCC;
background: #A00;
color: #FFF;
height:auto;
overflow:auto;
}
​.img{
float:right;
height:auto;
}​

<div class="intro">
    <div class="img"> <img src="http://1.bp.blogspot.com/_74so2YIdYpM/TEd09Hqrm6I/AAAAAAAAApY/rwGCm5_Tawg/s1600/tall+copy.jpg"    style="margin: 10px 10px; "/></div>

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</div>​​​​​​​​​​

DEMO