css3实现border渐变色

 .box{

     width: 100px;

     height: 100px;

     border:10px solid #ddd;

     border-image: -webkit-linear-gradient(#ddd,#000) 30 30;

     border-image: -moz-linear-gradient(#ddd,#000) 30 30;

     border-image: linear-gradient(#ddd,#000) 30 30;

}