Replace sprites.gif with header-bkg.png

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@2116 44740490-163a-0410-bde0-09ae8108e29a

www/resources/default.css

@@ -107,7 +107,7 @@ dt {
 }
 
 #header {
-	background: #666 url("sprites.gif") repeat-x 0 100%;
+	background: #666 url("header-bkg.png") repeat-x 0 100%;
 	margin: 0px;
 	padding: 0 0 8px;
 }