Images in ie are pixelated

问题

I've uploaded png images to a website, and they appear perfect in firefox, chrome and safari but they look horrible in ie. I have saved the files from photoshop, and they have a feature under image size that gives you the option to have the image as: bicubic automatic, bicubic sharper, bicubic smoother, bicubic, bilinear and nearest neighbor. Would any of these help?

html:

<ul class="social">
  <li><a target="_blank" href="https://plus.google.com/+ToadhallcottagesCoUk/posts"><img onmouseout=this.src='/images/googleplusgrey-flat.png' onmouseover=this.src='/images/googleplus-flat.png' src="/images/googleplusgrey-flat.png" width="38" height="38" alt="Toad Hall Cottages Google Plus Page"</a></li>
  <li><a target="_blank" href="http://www.twitter.com/thcottages"><img onmouseout=this.src='/images/twittergrey-flat.png' onmouseover=this.src='/images/twitter-flat.png' src="/images/twittergrey-flat.png" width="38" height="38" alt="Toad Hall Cottages on Twitter" /></a></li>
  <li><a target="_blank" href="http://www.facebook.com/holidaycottages"><img <img onmouseout=this.src='/images/facebookgrey-flat.png' onmouseover=this.src='/images/facebook-flat.png'  src="/images/facebookgrey-flat.png" width="38" height="38" alt="Toad Hall Cottages Facebook page"/></a></li>
  <li><a target="_blank" href="http://www.pinterest.com/thcottages/"><img <img onmouseout=this.src='/images/pinterestgrey-flat.png' onmouseover=this.src='/images/pinterest-flat.png' src="/images/pinterestgrey-flat.png" width="38" height="38" alt="Toad Hall Cottages Facebook page" /></a></li>
</ul>

css:

img.icon { 
  vertical-align: middle; 
  margin-right: 8px; 
  margin-left: 2px;
  image-rendering:optimizeSpeed;             /* Legal fallback */
  image-rendering:-moz-crisp-edges;          /* Firefox        */
  image-rendering:-o-crisp-edges;            /* Opera          */
  image-rendering:-webkit-optimize-contrast; /* Safari         */
}