Sharing in case anyone stumbles across this, as it took me a little while to track down (I didn’t find a matching post on a search).
If you have Tracking Prevention set to ‘Strict’ in Edge, you may find that the Facebook button widget fails ungracefully:
This appears to be because the widget is loaded within an iframe and Edge’s strict setting causes it to fail (the ugly grey is from the dynamically generated “This page has been blocked by Microsoft Edge” child div). If you take the url for the facebook likes plugin and paste it directly into an Edge tab, it works fine and you get the button, however.
Strict tracking prevention on Firefox seems to fail gracefully, as the entire widget is simply hidden. You lose the button, but at least the user experience is smoother.
Chrome doesn’t have a directly equivalent setting, but if you block ALL cookies, the widget still renders as normal. No issue there.
As more and more users start using stricter privacy settings, it’s more likely that our web site visitors may be among them, so it’s worth testing your site with strict settings to check it renders acceptably. Despite the disclaimer in the settings page that “this setting may break web site functionality”, most end-users won’t realise it’s their settings that’s the issue, and will instead assume your site is pants