make background image full width
html {
height: 100%;
}
body {
color: #999;
background: url('../images/background/main_bg.jpg') no-repeat center center fixed;
font-family: 'Roboto', sans-serif;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}