Favicons are small icons that are being often displayed in the browser address bar, stored with bookmarked pages, etc. You should only use the officialy approved favicons.
Add the following lines to the <head> section of your page:
<link rel="apple-touch-icon-precomposed" sizes="152x152" href="http://cdn.wfp.org/apple-touch-icon-152x152-precomposed.png" />
<link rel="apple-touch-icon-precomposed" sizes="144x144" href="http://cdn.wfp.org/apple-touch-icon-144x144-precomposed.png" />
<link rel="apple-touch-icon-precomposed" sizes="120x120" href="http://cdn.wfp.org/apple-touch-icon-120x120-precomposed.png" />
<link rel="apple-touch-icon-precomposed" sizes="114x114" href="http://cdn.wfp.org/apple-touch-icon-114x114-precomposed.png" />
<link rel="apple-touch-icon-precomposed" sizes="76x76" href="http://cdn.wfp.org/apple-touch-icon-76x76-precomposed.png" />
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="http://cdn.wfp.org/apple-touch-icon-72x72-precomposed.png" />
<link rel="apple-touch-icon-precomposed" href="http://cdn.wfp.org/apple-touch-icon-precomposed.png" />
<link rel="shortcut icon" href="http://cdn.wfp.org/favicon.ico" />