<!DOCTYPE html>
<html>
<head>
<style>
    a:focus {
        background: yellow;
    }
</style>
<script>
    function runTest() {
        document.getElementById("a3").focus();
    }
</script>
</head>
<body onload='runTest();'>
<a id="a1" href="#">1</a>
<a id="a2" href="#">2</a>
<a id="a3" href="#">3</a>
</body>
</html>