Koeklin has the answer.

Bonjour

Redirect code:

<script type="text/javascript">
var url ='../../pagename.html';
var delay = 4;
var d = delay * 1000;window.setTimeout ('parent.location.replace(url)', d);
</script>

Replace ../../pagename.html by the path or the URL of your page,
and change thenumber of sec. (4 is the number of sec. here).

via Apple – Support – Discussions – Landing page/splash screen auto ….