4.9

从上到下渐变：

#grad { background-image: linear-gradient(#e66465, #9198e5); }

从左到右的线性渐变：

#grad { height: 200px; background-image: linear-gradient(to right, red , yellow); }

从左上角到右下角的线性渐变：

#grad { height: 200px; background-image: linear-gradient(to bottom right, red, yellow); }