IE6 PNG替换:如何使嵌套的<a>可单击?

为了这个问题的目的,考虑一下:

<div class="has_transparent_png">
    <a href="foo.html">
        <span>
            <img src="logo.jpg" />
        </span>
    </a>
</div>

问题是: 在IE6中 <a>

.has_transparent_png {
    background-image: url(images/transparentpng.png);
}

* html .has_transparent_png {
    behavior: expression((this.runtimeStyle.behavior="none")&&(this.pngSet?this.pngSet=true:(this.nodeName == "IMG" && this.src.toLowerCase().indexOf('.png')>-1?(this.runtimeStyle.backgroundImage = "none", this.runtimeStyle.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + this.src + "', sizingMethod='image')", this.src = "images/spacer.gif"):(this.origBg = this.origBg? this.origBg :this.currentStyle.backgroundImage.toString().replace('url("', '').replace('")', ''), this.runtimeStyle.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + this.origBg + "', sizingMethod='crop')", this.runtimeStyle.backgroundImage = "none")), this.pngSet=true));
}

我怎么才能做这个 <