To fix that and allow PNG transparencies in IE6 i used to use a background-image:

PNG TRANSPARENCY FILTER WITH BACKGROUND-IMAGE

#logo {
    position: absolute;
    top: 25px;
    left: 25px;
    width: 214px;
    height: 34px;
    background-image: url('path_to_image/logo.png') !important;
    background-color: transparent;
    background-repeat: no-repeat;
    background-image: none;
    filter: none !important;
    filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src='path_to_image/logo.png', sizingMethod='crop');
}

HOW CAN YOU PUT A LINK IN THE IMAGE WITH THIS METHOD?

<div id="logo" onclick="window.location='/' "></div>

*  If you want the background-image seems as image link, you must set the style  “cursor: pointer” in the div

#content {
        min-height: 420px;
        height: auto !important;
        height: 420px;
}