[generator-webapp] autoprefixer:dist, running grunt serve, and this issue keeps occurring

main.css

body {
    padding-top: 70px; /* Required padding for .navbar-fixed-top. Change if height of navigation changes. */
}


.navbar-fixed-top .nav {
    padding: 15px 0;
}

.navbar-fixed-top .navbar-brand {
    padding: 0 15px;

}

@media(min-width:768px) {
    body {
        padding-top: 100px; /* Required padding for .navbar-fixed-top. Change if height of navigation changes. */
    }

    .navbar-fixed-top .navbar-brand {
        padding: 15px 0;
    }
}
/*profile pic*/


/*Begining of listing images*/
ul.rig {
  list-style: none;
  font-size: 0px;
  margin-left: -2.5%; /* should match li left margin */
}
ul.rig li {
  display: inline-block;
  padding: 10px;
  margin: 0 0 2.5% 2.5%;
  background: #fff;
  border: 1px solid #ddd;
  font-size: 16px;
  font-size: 1rem;
  vertical-align: top;
  box-shadow: 0 0 5px #ddd;
  box-sizing: border-box;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
}
ul.rig li img {
  max-width: 100%;
  height: auto;
  margin: 0 0 0px;
}
ul.rig li h3 {
  margin: 0 0 5px;
  text-align: center;
}
ul.rig li p {
 margin: 0 0 5px;
  text-align: center; 
}
}
/* class for 2 columns */
ul.rig.columns-2 li {
  width: 47.5%; /* this value + 2.5 should = 50% */
}
/* class for 3 columns */

/* class for 4 columns */

 
@media (max-width: 768px) {
  ul.grid-nav li {
    display: block;
    margin: 0 0 5px;
  }
  ul.grid-nav li a {
    display: block;
  }
  ul.rig {
    margin-left: 0;
  }
  ul.rig li {
    width: 100% !important; /* over-ride all li styles */
    margin: 0 0 20px;
  }
}
/*Nav bar toggle*/
.navbar-toggle{
  background-color: #84BCDF;
}
.navbar-default{
    background-color: white;  
}