issue with border / layout settings

I am trying to get rid of the border around the fb like widget. The specific css which I am trying to get rid of is:

._4s7c {
border: 1px solid #aaa;
border-top-color: #315c99;
}

I have tried this in the template css, which does not fix the issue:

._4s7c {
border: 0 !important;
}

Next I tried Adding a container div to fix the problem but the changes I apply to Layout Settings are not affecting the widget.

Please help! Thanks

https://ww.wp.xz.cn/plugins/facebook-button-plugin/