Load External CSS Styles Based on User Agent. Use for mobile CSS loading (saves loading time).

script.js

// Check if iPhone or iPod
if ((navigator.userAgent.match(/iPhone/i)) || (navigator.userAgent.match(/iPod/i))) {
    var cssPath = "http://path.to/iPhone.css";
}

// Check if Android 
if ((navigator.userAgent.match(/Android/i))) {
    var cssPath = "http://path.to/Android.css";
}

// Load CSS file
if (cssPath) {
    var head = document.getElementsByTagName('head')[0];
    var link = document.createElement('link');
    link.rel = 'stylesheet';
    link.type = 'text/css';
    link.href = cssPath;
    link.media = 'all';
    head.appendChild(link);
}​

Just a heads up... There's an irregular character on the last bracket of your code that causes a syntax error.