simple css failed to load in the run

** the below code is not working and I don't know why as I tried to use simple way but I failed

you can find the CSS is very simple and the HTML the same **

    <style>
    .gradient{

        background:linear-gradient(#ffffff,#d3d8e8);

    }

    .gridient .gradientcontent{

        margin: 0 auto;
        width: 980px;
        display: table;
    }

    .gridient .gradientcontent .worldmap{

        float: left;

    }

    .gridient .gradientcontent .worldmap .worldmapcontent {

        margin-right: 15px;
    }

    </style>
<div class="gradient">
  <div class="gradientcontent">
    <div class="worldmap">
      <div class="worldmapcontent">
        <div class="worldmapcontenttxt">
          Facebook helps you connect and share with the people in
          your life.
        </div>
      </div>
    </div>
  </div>
</div>