Keep background image fixed during scroll using css

Just add background-attachment to your code

body {
    background-position: center;
    background-image: url(../images/images5.jpg);
    background-attachment: fixed;
}

background-image: url("/your-dir/your_image.jpg");
min-height: 100%;
background-repeat: no-repeat;
background-attachment: fixed;
background-position: center;
background-size: cover;}

background-attachment: fixed;

http://www.w3.org/TR/CSS21/colors.html#background-properties