.radial-gradient {
    position:fixed;
    top:0px;
    left:0px;
    height:100%;
    width:100%;

    /*Fallback if gradeints don't work */
    background: #ff0000;
    /*Linear gradient... */
    background:
      radial-gradient(
       at center, #ff0000, #0000ff
      );
  }