mozilla-release/layout/style/test/visited_image_loading_frame_empty.html

<!DOCTYPE HTML>
<title>Test for :visited image loading</title>
<style type="text/css">

:link { background-color: blue }
:visited { background-color: purple }

#link:link       { background-image: url("visited_image_loading.sjs?1l"); }
#link:visited    { background-image: url("visited_image_loading.sjs?1v"); }
#visited:link    { background-image: url("visited_image_loading.sjs?2l"); }
#visited:visited { background-image: url("visited_image_loading.sjs?2v"); }

</style>
<a id="link" href="do-not-visit-this-link.html"></a>
<a id="visited" href="visited_image_loading_frame_empty.html"></a>