CSS to create a full width container inside a fixed width container. Works on IE9 and above.

full_width.html

<div class="container" style="width: 750px; margin: 0 auto;">
  <div class="row-full">
  --- Full width container ---
  </div>
</div>

style.css

.row-full{
  width: 100vw;
  position: relative;
  margin-left: -50vw;
  height: 100px;
  margin-top: 100px;
  left: 50%;
}