Stretch and scale a CSS image in the background - with CSS only

Question

I want that my background image stretch and scale depending on the browser viewport size.

I\'ve seen some questions on Stack Overflow that do the job, like

Answer 1

CSS:

html,body {
    background: url(images/bg.jpg) no-repeat center center fixed;
    -webkit-background-size: cover; /* For WebKit*/
    -moz-background-size: cover;    /* Mozilla*/
    -o-background-size: cover;      /* Opera*/
    background-size: cover;         /* Generic*/
}