Tribute page - first webpage

why wont the buttons center?

Why do you use ‘col-m-6’ in div ?

Bootstrap have class >> col-md-6

<div class="container row" id="social">
    <div class="col-m-6">
  <button class="btn btn-primary">Like</button>
      </div>
    <div class="col-m-6">
      <button class="btn btn-primary">Share</button>
    </div>
    <div class="col-m-6">
      <button class="btn btn-primary">Join the Darkside</button>
    </div>
    </div>
  </div>