Apple recently fixed the error on iOS 8 where YouTube videos would not play on a WebApp (Why HTML5 video doesn\'t play in IOS 8 WebApp(webview)?). This error was fixed in iO
I was sent this answer from the Apple Support Communities. All I had to do was to add '-nocookie' after youtube in the src of the iframe
<!DOCTYPE html>
<head>
<meta charset="utf-8">
<meta name="apple-mobile-web-app-capable" content="yes" />
<title>HTML5 Video Standalone Test</title>
<style>
body {
margin:0;
}
</style>
</head>
<body>
<iframe width="700" height="394" src="//www.youtube-nocookie.com/embed/xspoREpBOhY?rel=0" frameborder="0" allowfullscreen></iframe>
</body>
</html>
It worked for me in my test app.