css3實現border漸變色

 .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;




}