There are a number of different icons and even splash screens that you can set for various devices. This answer goes through how to support them all.
Here are some snippets I have used with relevant links to where I gathered the information. See my blog for more information and more information about the ASP.NET MVC Boilerplate project template with all this built in right out of the box (Including sample image files).
Add the following mark-up to your html head. The commented out sections are entirely optional. While the uncommented sections are recommended to cover all icon usages. Don't be scared, most if it is comments to help you.
<!-- Icons & Platform Specific Settings - Favicon generator used to generate the icons below http://realfavicongenerator.net/ -->
<!-- shortcut icon - It is best to add this icon to the root of your site and only use this link element if you move it somewhere else. This file contains the following sizes 16x16, 32x32 and 48x48. -->
<!--<link rel="shortcut icon" href="favicon.ico">-->
<!-- favicon-96x96.png - For Google TV. -->
<link rel="icon" type="image/png" href="/content/images/favicon-96x96.png" sizes="96x96">
<!-- favicon-16x16.png - The classic favicon, displayed in the tabs. -->
<link rel="icon" type="image/png" href="/content/images/favicon-16x16.png" sizes="16x16">
<!-- favicon-32x32.png - For Safari on Mac OS. -->
<link rel="icon" type="image/png" href="/content/images/favicon-32x32.png" sizes="32x32">
<!-- Android/Chrome -->
<!-- manifest-json - The location of the browser configuration file. It contains locations of icon files, name of the application and default device screen orientation. Note that the name field is mandatory.
https://developer.chrome.com/multidevice/android/installtohomescreen. -->
<link rel="manifest" href="/content/icons/manifest.json">
<!-- theme-color - The colour of the toolbar in Chrome M39+
http://updates.html5rocks.com/2014/11/Support-for-theme-color-in-Chrome-39-for-Android -->
<meta name="theme-color" content="#1E1E1E">
<!-- favicon-192x192.png - For Android Chrome M36 to M38 this HTML is used. M39+ uses the manifest.json file. -->
<link rel="icon" type="image/png" href="/content/icons/favicon-192x192.png" sizes="192x192">
<!-- mobile-web-app-capable - Run Android/Chrome version M31 to M38 in standalone mode, hiding the browser chrome. -->
<!-- <meta name="mobile-web-app-capable" content="yes"> -->
<!-- Apple Icons - You can move all these icons to the root of the site and remove these link elements, if you don't mind the clutter.
https://developer.apple.com/library/safari/documentation/AppleApplications/Reference/SafariHTMLRef/Introduction.html#//apple_ref/doc/uid/30001261-SW1 -->
<!-- apple-mobile-web-app-title - The name of the application if pinned to the IOS start screen. -->
<!--<meta name="apple-mobile-web-app-title" content="">-->
<!-- apple-mobile-web-app-capable - Hide the browsers user interface on IOS, when the app is run in 'standalone' mode. Any links to other pages that are clicked whilst your app is in standalone mode will launch the full Safari browser. -->
<!--<meta name="apple-mobile-web-app-capable" content="yes">-->
<!-- apple-mobile-web-app-status-bar-style - default/black/black-translucent Styles the IOS status bar. Using black-translucent makes it transparent and overlays it on top of your site, so make sure you have enough margin. -->
<!--<meta name="apple-mobile-web-app-status-bar-style" content="black">-->
<!-- apple-touch-icon-57x57.png - Android Stock Browser and non-Retina iPhone and iPod Touch -->
<link rel="apple-touch-icon" sizes="57x57" href="/content/images/apple-touch-icon-57x57.png">
<!-- apple-touch-icon-114x114.png - iPhone (with 2× display) iOS = 6 -->
<link rel="apple-touch-icon" sizes="114x114" href="/content/images/apple-touch-icon-114x114.png">
<!-- apple-touch-icon-72x72.png - iPad mini and the first- and second-generation iPad (1× display) on iOS = 6 -->
<link rel="apple-touch-icon" sizes="72x72" href="/content/images/apple-touch-icon-72x72.png">
<!-- apple-touch-icon-144x144.png - iPad (with 2× display) iOS = 6 -->
<link rel="apple-touch-icon" sizes="144x144" href="/content/images/apple-touch-icon-144x144.png">
<!-- apple-touch-icon-60x60.png - Same as apple-touch-icon-57x57.png, for non-retina iPhone with iOS7. -->
<link rel="apple-touch-icon" sizes="60x60" href="/content/images/apple-touch-icon-60x60.png">
<!-- apple-touch-icon-120x120.png - iPhone (with 2× and 3 display) iOS = 7 -->
<link rel="apple-touch-icon" sizes="120x120" href="/content/images/apple-touch-icon-120x120.png">
<!-- apple-touch-icon-76x76.png - iPad mini and the first- and second-generation iPad (1× display) on iOS = 7 -->
<link rel="apple-touch-icon" sizes="76x76" href="/content/images/apple-touch-icon-76x76.png">
<!-- apple-touch-icon-152x152.png - iPad 3+ (with 2× display) iOS = 7 -->
<link rel="apple-touch-icon" sizes="152x152" href="/content/images/apple-touch-icon-152x152.png">
<!-- apple-touch-icon-180x180.png - iPad and iPad mini (with 2× display) iOS = 8 -->
<link rel="apple-touch-icon" sizes="180x180" href="/content/images/apple-touch-icon-180x180.png">
<!-- Apple Startup Images - These are shown when the page is loading if the site is pinned https://gist.github.com/tfausak/2222823 -->
<!-- apple-touch-startup-image-1536x2008.png - iOS 6 & 7 iPad (retina, portrait) -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-1536x2008.png"
media="(device-width: 768px) and (device-height: 1024px) and (orientation: portrait) and (-webkit-device-pixel-ratio: 2)">
<!-- apple-touch-startup-image-1496x2048.png - iOS 6 & 7 iPad (retina, landscape) -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-1496x2048.png"
media="(device-width: 768px) and (device-height: 1024px) and (orientation: landscape) and (-webkit-device-pixel-ratio: 2)">
<!-- apple-touch-startup-image-768x1004.png - iOS 6 iPad (portrait) -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-768x1004.png"
media="(device-width: 768px) and (device-height: 1024px) and (orientation: portrait) and (-webkit-device-pixel-ratio: 1)">
<!-- apple-touch-startup-image-748x1024.png - iOS 6 iPad (landscape) -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-748x1024.png"
media="(device-width: 768px) and (device-height: 1024px) and (orientation: landscape) and (-webkit-device-pixel-ratio: 1)">
<!-- apple-touch-startup-image-640x1096.png - iOS 6 & 7 iPhone 5 -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-640x1096.png"
media="(device-width: 320px) and (device-height: 568px) and (-webkit-device-pixel-ratio: 2)">
<!-- apple-touch-startup-image-640x920.png - iOS 6 & 7 iPhone (retina) -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-640x920.png"
media="(device-width: 320px) and (device-height: 480px) and (-webkit-device-pixel-ratio: 2)">
<!-- apple-touch-startup-image-320x460.png - iOS 6 iPhone -->
<link rel="apple-touch-startup-image"
href="/content/images/apple-touch-startup-image-320x460.png"
media="(device-width: 320px) and (device-height: 480px) and (-webkit-device-pixel-ratio: 1)">
<!-- Windows 8 Icons - If you add an RSS feed, revisit this page and regenerate the browserconfig.xml file. You will then have a cool live tile!
browserconfig.xml - Windows 8.1 - Has been added to the root of the site. This points to the tile images and tile background colour. It contains the following images:
mstile-70x70.png - For Windows 8.1 / IE11.
mstile-144x144.png - For Windows 8 / IE10.
mstile-150x150.png - For Windows 8.1 / IE11.
mstile-310x310.png - For Windows 8.1 / IE11.
mstile-310x150.png - For Windows 8.1 / IE11.
See http://www.buildmypinnedsite.com/en and http://msdn.microsoft.com/en-gb/library/ie/dn255024%28v=vs.85%29.aspx. -->
<!-- application-name - Windows 8+ - The name of the application if pinned to the start screen. -->
<!--<meta name="application-name" content="">-->
<!-- msapplication-TileColor - Windows 8 - The tile colour which shows around your tile image (msapplication-TileImage). -->
<meta name="msapplication-TileColor" content="#5cb95c">
<!-- msapplication-TileImage - Windows 8 - The tile image. -->
<meta name="msapplication-TileImage" content="/content/images/mstile-144x144.png">
My browserconfig.xml file. Full explanation above.
<?xml version="1.0" encoding="utf-8"?>
<browserconfig>
<msapplication>
<tile>
<square70x70logo src="/Content/Images/mstile-70x70.png"/>
<square150x150logo src="/Content/Images/mstile-150x150.png"/>
<square310x310logo src="/Content/Images/mstile-310x310.png"/>
<wide310x150logo src="/Content/Images/mstile-310x150.png"/>
<TileColor>#5cb95c</TileColor>
</tile>
</msapplication>
</browserconfig>
My manifest.json file. Full explanation above.
{
"name": "ASP.NET MVC Boilerplate (Required! Update This)",
"icons": [
{
"src": "\/Content\/icons\/android-chrome-36x36.png",
"sizes": "36x36",
"type": "image\/png",
"density": "0.75"
},
{
"src": "\/Content\/icons\/android-chrome-48x48.png",
"sizes": "48x48",
"type": "image\/png",
"density": "1.0"
},
{
"src": "\/Content\/icons\/android-chrome-72x72.png",
"sizes": "72x72",
"type": "image\/png",
"density": "1.5"
},
{
"src": "\/Content\/icons\/android-chrome-96x96.png",
"sizes": "96x96",
"type": "image\/png",
"density": "2.0"
},
{
"src": "\/Content\/icons\/android-chrome-144x144.png",
"sizes": "144x144",
"type": "image\/png",
"density": "3.0"
},
{
"src": "\/Content\/icons\/android-chrome-192x192.png",
"sizes": "192x192",
"type": "image\/png",
"density": "4.0"
}
]
}
A list of the files in the project (Note that the names of these files are important if you decide to put some of them at the root of your project to avoid using the above meta tags):
favicon.ico
browserconfig.xml
Content/Images/
android-chrome-144x144.png
android-chrome-192x192.png
android-chrome-36x36.png
android-chrome-48x48.png
android-chrome-72x72.png
android-chrome-96x96.png
apple-touch-icon.png
apple-touch-icon-57x57.png
apple-touch-icon-60x60.png
apple-touch-icon-72x72.png
apple-touch-icon-76x76.png
apple-touch-icon-114x114.png
apple-touch-icon-120x120.png
apple-touch-icon-144x144.png
apple-touch-icon-152x152.png
apple-touch-icon-180x180.png
apple-touch-icon-precomposed.png (180x180)
favicon-16x16.png
favicon-32x32.png
favicon-96x96.png
favicon-192x192.png
manifest.json
mstile-70x70.png
mstile-144x144.png
mstile-150x150.png
mstile-310x150.png
mstile-310x310.png
apple-touch-startup-image-1536x2008.png
apple-touch-startup-image-1496x2048.png
apple-touch-startup-image-768x1004.png
apple-touch-startup-image-748x1024.png
apple-touch-startup-image-640x1096.png
apple-touch-startup-image-640x920.png
apple-touch-startup-image-320x460.png
Total Overhead
If you take out the comments that's 3KB of extra HTML, if you don't support splash screens that's 1.5KB. If you are using GZIP compression on your HTML content, which everyone should be doing these days, that leaves you with about 634 Bytes of overhead per request to support all platforms or 446 Bytes without splash screens. I personally think its worth it to support IOS, Android and Windows devices but its your choice, I'm just giving the options!
Side Note About The Current Web Icon/Splash Screen/Settings Situation
This situation with vendor specific icons, splash screens and special tags to control the web browser or pinned icons is ridiculous. In a perfect world we would all use a favicon.svg file which could look good at any size and could be placed at the root of the page. Only FireFox supports this at the time of writing (See CanIUse.com).
However, icons are not the only setting these days, there are several other vendor specific settings (shown above) but a favicon.svg file would cover most use cases.
Update
Updated to include the new Android/Chrome version M39+ favicon/theming options. Interestingly, they have gone with a similar approach to Microsoft but are using a JSON file instead of XML.