You can create a responsive Facebook like box in WordPress or any other CMS platform or framework so that it sits in the sidebar or parent container at the correct 100% width which will just adjust to various device widths – all done in the CSS.

This is the CSS declarations to add in your CSS file.

Fill the parent container by 100% width.

.fb_iframe_widget {
	display: block !important;
}

.fb-like-box iframe {
 	width: 100% !important;
}

.fb-like-box span {
	width: auto !important;
	position: initial !important;
}
.fb_iframe_widget_fluid span {
	width:100% !important;
}
.fb_iframe_widget span {
	position: static !important;
}