CODE:
<public:component lightWeight="true">
<public:attach event="onpropertychange" onevent="propertyChanged()" />
<public:attach event="onbeforeprint" onevent="beforePrint()" for="window"/>
<public:attach event="onafterprint" onevent="afterPrint()" for="window"/>
<script>
/*
* PNG Behavior
*
* This script was created by Erik Arvidsson (http://webfx.eae.net/contact.html#erik)
* for WebFX (http://webfx.eae.net)
* Copyright 2002-2004
*
* For usage see license at http://webfx.eae.net/license.html
*
* Version: 1.02
* Created: 2001-??-?? First working version
* Updated: 2002-03-28 Fixed issue when starting with a non png image and
* switching between non png images
* 2003-01-06 Fixed RegExp to correctly work with IE 5.0x
* 2004-05-09 When printing revert to original
*
*/

var supported = /MSIE ((5\.5)|[6789])/.test(navigator.userAgent) &&
navigator.platform == "Win32";

var realSrc;
var blankSrc = "blank.gif";
var isPrinting = false;

if (supported) fixImage();

function propertyChanged() {
if (!supported || isPrinting) return;
var pName = event.propertyName;
if (pName != "src") return;
// if not set to blank
if (!new RegExp(blankSrc).test(src))
fixImage();
};

function fixImage() {
// get src
var src = element.src;
// check for real change
if (src == realSrc && /\.png$/i.test(src)) {
element.src = blankSrc;
return;
}

if ( ! new RegExp(blankSrc).test(src)) {
// backup old src
realSrc = src;
}
// test for png
if (/\.png$/i.test(realSrc)) {
// set blank image
element.src = blankSrc;
// set filter
element.runtimeStyle.filter = "progid:DXImageTransform.Microsoft." +
"AlphaImageLoader(src='" + src + "',sizingMethod='scale')";
}
else {
// remove filter
element.runtimeStyle.filter = "";
}
}

function beforePrint() {
isPrinting = true;
element.src = realSrc;
element.runtimeStyle.filter = "";
realSrc = null;
}

function afterPrint() {
isPrinting = false;
fixImage();
}
</script>
</public:component>

CODE:
img {
behavior: url("pngbehavior.htc");
}