Üzerine gelince saydamlığı değişen resim

<style type="text/css">

/*Credits: Dynamic Drive CSS Library */
/*URL: http://www.dynamicdrive.com/style/ */

.toggleopacity img{
filter:progid:DXImageTransform.Microsoft.Alpha(opacity=50);
-moz-opacity: 0.5;
}

.toggleopacity:hover img{
filter:progid:DXImageTransform.Microsoft.Alpha(opacity=100);
-moz-opacity: 1;
}

.toggleopacity img{
border: 1px solid #ccc;
}

.toggleborder:hover img{
border: 1px solid navy;
}

.toggleborder:hover{
color: red; /* Dummy definition to overcome IE bug */
}

</style>

<a class="toggleopacity" href="http://www.dynamicdrive.com">
<img border="0" src="media/button.gif" width="137" height="26" />
</a>

<a class="toggleborder" href="http://www.dynamicdrive.com/style/">
<img border="0" src="media/button2.gif" width="163" height="57" />
</a>