when give inside div top margin move out sider div

.main-con{
    width:960px;
    background-color:ffffff;
    margin-left:auto;
    margin-right:auto;
    }

.box {
  position: relative;
  width: 800px;
  height: 300px;
  background-color: #fff;
  margin-right:auto;
  margin-left:auto;
  border-bottom:1px #CCCCCC solid;

}
.box:before {
    position: absolute;
    width: 800px;
    border-bottom:1px #CCCCCC solid;
    border-radius: 10px / 100px;
    z-index: -1;
    top: 10%;
    bottom: 10%;
    content: "";
    box-shadow: 0 0 15px rgba(0,0,0,0.6);
    }

.top-stripe{
    height:80px;
    margin-top:60px;
    background: rgb(160,29,99); /* Old browsers */
background: -moz-linear-gradient(left, rgba(160,29,99,1) 0%, rgba(217,0,115,1) 30%, rgba(217,0,115,1) 70%, rgba(160,29,99,1) 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, right top, color-stop(0%,rgba(160,29,99,1)), color-stop(30%,rgba(217,0,115,1)), color-stop(70%,rgba(217,0,115,1)), color-stop(100%,rgba(160,29,99,1))); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(left, rgba(160,29,99,1) 0%,rgba(217,0,115,1) 30%,rgba(217,0,115,1) 70%,rgba(160,29,99,1) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(left, rgba(160,29,99,1) 0%,rgba(217,0,115,1) 30%,rgba(217,0,115,1) 70%,rgba(160,29,99,1) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(left, rgba(160,29,99,1) 0%,rgba(217,0,115,1) 30%,rgba(217,0,115,1) 70%,rgba(160,29,99,1) 100%); /* IE10+ */
background: linear-gradient(to right, rgba(160,29,99,1) 0%,rgba(217,0,115,1) 30%,rgba(217,0,115,1) 70%,rgba(160,29,99,1) 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#a01d63', endColorstr='#a01d63',GradientType=1 ); /* IE6-9 */


    }

<div class="box">
        <div class="top-stripe"></div>
    </div>