#box{
width:500px;
height:500px;
background: -webkit-linear-gradient(bottom,red,yellow);
background: -moz-linear-gradient(bottom,red,yellow);
background: -ms-linear-gradient(bottom,red,yellow); 
background: -o-linear-gradient(bottom,red,yellow);
}


 */   use TOP, BOTTOM, LEFT, RIGHT for gradient direction     */