[Octane]

<style>
body {
   background: #fff;
}
.image {
   position: absolute;
   width: 336px;
   height: 76px;
   background: #fff;
}
#img1 {
   top: 0;
   left: 0;
}
#img2 {
   top: 38px;
   left: 168px;
}
.image img {
   vertical-align: top;
   opacity: 0.3;
}
.image img:hover {
   opacity: 1;
}
</style>
<div class="image" id="img1"><img src="http://javascript.ru/forum/images/ca_serenity/misc/logo.gif" alt="…" width="336" height="76"></div>
<div class="image" id="img2"><img src="http://javascript.ru/forum/images/ca_serenity/misc/logo.gif" alt="…" width="336" height="76"></div>