a écrit :

When I click the Like button, the popup window (or "flyout") doesn't show. Why?

If the Like button is placed near the edge of an HTML element with the overflow property set to hidden, the flyout may be clipped or completely hidden when the button is clicked. This can be remedied by setting setting the overflow property to a value other than hidden, such as visible, scroll, or auto.

.fb_edge_widget_with_comment span.fb_edge_comment_widget {
    top: -150px !important;
}

<script>
        (function(d, s, id) {
	var js, fjs = d.getElementsByTagName(s)[0];
	if (d.getElementById(id)) return;
	js = d.createElement(s); js.id = id;
	js.src = "//connect.facebook.net/fr_FR/all.js#xfbml=1";
	fjs.parentNode.insertBefore(js, fjs);
	}(document, 'script', 'facebook-jssdk'));
</script>