Ho provato ad creare un Like Button di Facebook in un file html con questo doctype:
codice HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
ma non vedo nulla. Ecco qui sotto le diverse opzioni che mi propone facebook:
HTML 5
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>eeee</title>
</head>
<body>
<div id="fb-root"></div>
<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/it_IT/sdk.js#xfbml=1&version=v2.0";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>
<div class="fb-like-box" data-href="https://www.facebook.com/HTML.it" data-width="400" data-height="400" data-colorscheme="light" data-show-faces="true" data-header="true" data-stream="false" data-show-border="true"></div>
</body>
</html>
IFRAME
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>eeee</title>
</head>
<body>
<iframe src="//www.facebook.com/plugins/likebox.php?href=https%3A%2F%2Fwww.facebook.com%2FHTML.it&width=400&height=290&colorscheme=light&show_faces=true&header=true&stream=false&show_border=true" scrolling="no" frameborder="0" style="border:none; overflow:hidden; width:400px; height:290px;" allowTransparency="true"></iframe>
</body>
</html>
XFBML
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<html xmlns:fb="http://ogp.me/ns/fb#">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>eeee</title>
</head>
<body>
<div id="fb-root"></div>
<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/it_IT/sdk.js#xfbml=1&version=v2.0";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>
<fb:like-box href="https://www.facebook.com/HTML.it" width="400" height="400" colorscheme="light" show_faces="true" header="true" stream="false" show_border="true"></fb:like-box>
</body>
</html>
Le ho provate tutte ma non funzionano... 
Questa è la pagina che uso:
https://developers.facebook.com/docs...-box-for-pages