Orientation for <meta> viewport?

The full specification and its under-implementation.

Apple invented the viewport meta key to “improve the presentation of your web content on iOS.” Many of the popular mobile browsers followed with implementations, including the Android Browser, Chrome for Android, Safari Mobile, Firefox for Mobile or Opera Mobile.

<meta name="viewport" content="width=device-width,user-scalable=no" />

While W3C specifications are still in draft as of May 2013, the “orientation” property was even published in the original 2011 draft.

The proposed “orientation” descriptor would allow the author to “request that a document is displayed in portrait or landscape mode.”

<meta name="viewport" content="orientation=portrait" />

Add this to the list of aspects for which HTML5 web apps still fall short of native apps.