Hello

I try change the image with this code css, but don't worked. Any suggestions?

Code:
@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document domain('sitepoint.com') {

img[src*="forum_new-48.png"] {
	background: url("http://imageshack.us/scaled/landing/94/k1x3pv.png") no-repeat !important;   
}
}
Result:

BRiC1.png

Thanks!