Alternate CSS for iPhone 4s

I need to have some alternate styles for the iPhone 4s.
But I can’t figure out how.

fugostudios.com

I tried this code, but it doesn’t seem to affect anything.

<link rel="stylesheet" type="text/css" media="all" href="<?php bloginfo( 'stylesheet_url' ); ?>" />

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_mobile.css"
media="only screen and (min-device-width : 320px) and (max-device-width : 480px)"> 

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_mobile.css"
media="only screen and (min-width : 321px)"> 

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_mobile.css"
media="only screen and (max-width : 320px)"> 

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_ipad.css"
media="only screen and (min-device-width : 768px) and (max-device-width : 1024px)"> 

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_ipad.css"
media="only screen and (min-device-width : 768px) and (max-device-width : 1024px) and (orientation : landscape)"> 

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_ipad.css"
media="only screen and (min-device-width : 768px) and (max-device-width : 1024px) and (orientation : portrait)"> 

<link rel="stylesheet" href="<?php bloginfo('url'); ?>/style_mobile.css"
media="only screen and (-webkit-min-device-pixel-ratio : 1.5), only screen and (min-device-pixel-ratio : 1.5)">