add linear gradient with url in css code example

Example: background-image linear-gradient url

body {
    background-image: url("http://www.skrenta.com/images/stackoverflow.jpg"), linear-gradient(red, yellow);
    background-image: url("http://www.skrenta.com/images/stackoverflow.jpg"), -webkit-gradient(linear, left top, left bottom, from(red), to(yellow));
    background-image: url("http://www.skrenta.com/images/stackoverflow.jpg"), -moz-linear-gradient(top, red, yellow);
  }