viewport meta tag

https://developer.mozilla.org/en-US/docs/Mobile/Viewport_meta_tag

http://www.paulund.co.uk/understanding-the-viewport-meta-tag

http://blog.javierusobiaga.com/stop-using-the-viewport-tag-until-you-know-ho

http://webdesign.tutsplus.com/tutorials/htmlcss-tutorials/quick-tip-dont-forget-the-viewport-meta-tag/