CSS Media Queries for iPhone 3, iPhone 4, iPhone 4S and iPhone 5

iPhone 5 Media Queries
iPhone 5 in portrait & landscape

@media only screen
and (min-device-width : 320px)
and (max-device-width : 568px) { /* STYLES GO HERE */}

iPhone 5 in landscape

@media only screen
and (min-device-width : 320px)
and (max-device-width : 568px)
and (orientation : landscape) { /* STYLES GO HERE */}

iPhone 5 in portrait

@media only screen
and (min-device-width : 320px)
and (max-device-width : 568px)
and (orientation : portrait) { /* STYLES GO HERE */ }

iPhone 2G, 3G, 4, 4S Media Queries

It's noteworthy that these media queries are also the same for iPod Touch generations 1-4.
iPhone 2G-4S in portrait & landscape

@media only screen
and (min-device-width : 320px)
and (max-device-width : 480px) { /* STYLES GO HERE */}

iPhone 2G-4S in landscape

@media only screen
and (min-device-width : 320px)
and (max-device-width : 480px)
and (orientation : landscape) { /* STYLES GO HERE */}

iPhone 2G-4S in portrait

@media only screen
and (min-device-width : 320px)
and (max-device-width : 480px)
and (orientation : portrait) { /* STYLES GO HERE */ }

iPhone 5 Resolution

Screen Width = 320px (CSS Pixels)
Screen Height = 568px (CSS Pixels)

Screen Width = 640px (Actual Pixels)
Screen Height = 1136px (Actual Pixels)

Device-pixel-ratio: 2

iPhone 4/4S Resolution

Screen Width = 320px (CSS Pixels)
Screen Height = 480px (CSS Pixels)

Screen Width = 640px (Actual Pixels)
Screen Height = 960px (Actual Pixels)

Device-pixel-ratio: 2

iPhone 2G/3G/3GS Resolution

Screen Width = 320px (CSS Pixels)
Screen Height = 480px (CSS Pixels)

Screen Width = 320px (Actual Pixels)
Screen Height = 480px (Actual Pixels)

Device-pixel-ratio: 1