If this is your first exposure to responsive web design, you'll notice that most of your custom styles will be in the default section. The other sections are for overriding your default styles to tweak for other device widths and resolutions. The Horizontal Tweaks section is for overriding styles for landscape orientation. The iPad section is geared for tablet resolutions between the 768px parameter and the 1024px parameter. In the HD and Retina Tweaks section, you will most likely be only overriding background image styles to substitute higher resolution graphics. We'll soon see examples of these in action, and put what we use into /css/custom.css. In the mean time, just look at the following structures:
/* CSS Document */
/* Default Styles -------------*/
/* Horizontal Tweaks ----------*/
@media all and (min-width: 480px){
}
/* HD and Retina Tweaks ---------*/
@media only screen and (-webkit-min-device-pixel-ratio: 1.2),
only screen and (min--moz...