How to override CSS?

This is my website : http://www.ville-torcy.fr/

As you can see, facebook part is not well aligned :

I inspected it with Google Chrome and found this :

<div class="_2p3a" style="min-width: 180px; width: 270px;">

It should be :

<div class="_2p3a" style="min-width: 160px; width: 188px;">

But how to change it? It's a css from facebook. I tried to override it like that:

Added this line in my style.css, it doesn't work :

._2p3a {
min-width: 160px !important; 
width: 188px !important;
}

It should look like that : https://www.dropbox.com/s/tabanivbvg7v749/Capture%20d%27%C3%A9cran%202016-06-11%2018.59.43.png?dl=0

Thanks for you help