set div width by background image code example
Example 1: how to set background image 100 height
html {
background: url(images/bg.jpg) no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}
Example 2: how to change the width of a background image in css
#example1 { /* Example1 has an auto background size */
background: url(mountain.jpg);
background-repeat: no-repeat;
background-size: auto;
}
#example2 { /* Example2 has an fixed background size */
background: url(mountain.jpg);
background-repeat: no-repeat;
background-size: 300px 100px;
}