#altmenu{
position: absolute;
bottom: 0px;
right: 0px;
text-indent: -1000px;
width: 100px;
height: 85px;
overflow: hidden;
background: url(demo.gif) 0 0 no-repeat;
}

<a href="http://iteadresi" target="_blank" title="Resim üstüne gelince çıkan text" id="altmenu"></a>