Background-Image fallback image

HTML

<span></span>

CSS

span{ 
display:block; 
width:146px; 
height:135px; 
background: transparent url("http://dev.bowdenweb.com/pro/watkins/i/1aac.png") 0 0 no-repeat; 
background-image:url("http://dev.bowdenweb.com/pro/watkins/i/1aad.png");
}