Change the desktop css media query to:
@media only screen and (min-width: 769px) {
body {
margin: 0;
padding: 0;
}
.gridContainer {
width: 100%;
margin: auto;
padding: 0;
}
#LayoutDiv1 {
clear: both;
float: left;
margin-left: 0;
width: 100%;
display: block;
}
}