how to add a rainbow in css background code example

Example: css background rainbow

#grad1 {
    height: 200px;
    background: red; /* For browsers that do not support gradients */
    background: -webkit-linear-gradient(left, orange , yellow, green, cyan, blue, violet); /* For Safari 5.1 to 6.0 */
    background: -o-linear-gradient(right, orange, yellow, green, cyan, blue, violet); /* For Opera 11.1 to 12.0 */
    background: -moz-linear-gradient(right, orange, yellow, green, cyan, blue, violet); /* For Firefox 3.6 to 15 */
    background: linear-gradient(to right, orange , yellow, green, cyan, blue, violet); /* Standard syntax (must be last) */
}