WEB GRADIENTS.COM code example

Example 1: uigradients

background: #0f2027; /* fallback for old browsers */
  background: -webkit-linear-gradient(to right, #0f2027, #203a43, #2c5364); /* Chrome 10-25, Safari 5.1-6 */
  background: linear-gradient(to right, #0f2027, #203a43, #2c5364); /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */

Example 2: gradient

Here a codePen with cool gradient animations:
https://codepen.io/DevLorenzo/pen/ExgpvJM