Head stuff

<link rel="shortcut icon" type="image/x-icon" href="/favicon.ico">
<link rel="shortcut icon" type="image/png" href="/favicon.png">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

iPhone viewport

<meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0">
<meta name="viewport" content="width=device-width">
<meta name="viewport" content="width=320, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"/> <!-- full example -->

Default OpenGraph meta tags

<meta content="..." name="description">
<meta content="..." property="og:description">
<meta content="http://.../preview.jpg" property="og:image">
<meta content="Hello There" property="og:title">
<meta content="Hello There" property="og:site_name">
<meta content="hellothere" property="fb:admins">
<meta content="website" property="og:type">

Webfonts

<script>WebFontConfig={    },function(a,b){var c=a.createElement(b);c.src="//ajax.googleapis.com/ajax/libs/webfont/1/webfont.js",c.async=1;var d=a.getElementsByTagName(b)[0];d.parentNode.insertBefore(c,d)}(document,"script")</script>

// {typekit{id:"..."}}
// {google:{families:['Exo:400']}}

Google Analytics

<script>location.hostname.match(/helloworld\.com/)&&(_gaq=[["_setAccount","UA-XXXXX-1"],["_trackPageview"]],function(a,b){var c=a.createElement(b),d=a.getElementsByTagName(b)[0];c.async=1,c.src=("https:"==location.protocol?"//ssl":"//www")+".google-analytics.com/ga.js",d.parentNode.insertBefore(c,d)}(document,"script"))</script>

FB/Twitter

<div id="fb-root"></div><script>fbAsyncInit=function(){FB.init({"appId":"___APPIDGOESHERE___","status":true,"cookie":true,"xfbml":true})};!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.async=1;js.src='//connect.facebook.net/en_US/all.js';fjs.parentNode.insertBefore(js,fjs);}}(document,'script','facebook-jssdk');</script>

<script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.async=1;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script>

HTML5 Shiv for IE8

<!--[if lte IE 8]><script src='//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.6.1/html5shiv.js'></script><![endif]-->

H5BP HTML tag (IE8 and IE9 only)

<!--[if lte IE 8]><html class="ie8"><![endif]--><!--[if IE 9]><html class="ie9"><![endif]--><!--[if gt IE 9]><!-->
<html><!--<![endif]-->

Touch icons

Icons

<link rel="shortcut icon" type="image/png" href="favicon.png">
<link href="apple-touch-icon-precomposed.png" rel="apple-touch-icon">
<link href="apple-touch-icon-57x57-precomposed.png" size="57x57" rel="apple-touch-icon">
<link href="apple-touch-icon-72x72-precomposed.png" size="72x72" rel="apple-touch-icon">
<link href="apple-touch-icon-114x114-precomposed.png" size="114x114" rel="apple-touch-icon">
<link href="apple-touch-icon-144x144-precomposed.png" size="144x144" rel="apple-touch-icon">

Only do this if you’re not placing the site in the root!

H5BP HTML tag

<!--[if lt IE 7 ]> <html class="ie6"> <![endif]-->
<!--[if IE 7 ]>    <html class="ie7"> <![endif]-->
<!--[if IE 8 ]>    <html class="ie8"> <![endif]-->
<!--[if IE 9 ]>    <html class="ie9"> <![endif]-->
<!--[if (gt IE 9)|!(IE)]><!--> <html class=""> <!--<![endif]-->

Google jQuery

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

Unsupported message

<!--[if lt IE 8]>
<div class="unsupported-browser">
  <strong>
    You are using an outdated browser.
  </strong>
  <span>
    Please <a class="upgrade-browser"
    href="http://browsehappy.com/">
    upgrade your browser</a> or <a  class="chrome-frame"
    href="http://www.google.com/chromeframe/?redirect=true">activate Google 
    Chrome Frame</a> to improve your experience.
  </span>
</div>
<![endif]-->

HTML Compatibility inspector

<script src="http://ie.microsoft.com/testdrive/HTML5/CompatInspector/inspector.js"></script>

More info here: microsoft.com