That's a valid error, and one our Autotune Error Check tool is alerting you too as well. If you run it, you should see the following error:
Test: Facebook Javascript library inclusion
Fail: Another Facebook extension is installed, including the Facebook Javascript library, and may conflict.
Looking at the HTML on your site is the following bit of code:
<!-- Facebook SDK -->
<div id='fb-root'></div>
<script type='text/javascript'>
// Load the SDK Asynchronously
(function(d){
var js, id = 'facebook-jssdk'; if (d.getElementById(id)) {return;}
js = d.createElement('script'); js.id = id; js.async = true;
js.src = '//connect.facebook.net/nb_NO/all.js';
d.getElementsByTagName('head')[0].appendChild(js);
}(document));
</script>
<!-- End Facebook SDK -->Some extension, module or plugin on your site is adding the above block which is the old version of the Facebook Javascript Library. You'll need to narrow down and disable that extension to prevent the W3C error and conflicts that will happen within JFBConnect if it's left enabled.
I hope that helps get you going,
Alex
W3C validation error
