Issue with image auto resing…

Thanks,
Original width of my image is (680 × 330) ..
and in website the image place holder size is (560 x 170)
That why image looks like stretch … and we are using Full With option from media when we select image for feature image …

my code is

<div class=”blogimg”>

<img width=”560″ height=”170″ border=”0″ src=”http://pvlgnyc.com/wp-content/uploads/2013/02/DSC03062.jpg”&gt;

</div>

CSS

.blogimg {
margin: 10px 0 0 10px;
float: left;
height: auto;
padding-bottom: 10px;
width: 560px;
height: 170px;
}