У вашего броузера проблема в совместимости с HTML5
Learn the basic properties for using Flexbox. Flexbox is a set of properties that make it easy for us to control the layout of items in a container. Later on, we'll see how this helps us create navigation elements and center items in our layout.
Code:
http://codepen.io/brianhaferkamp/pen/PpXJLw/
Learn more about CSS Flexbox:
https://www.youtube.com/playlist?list=PLMklnyuK-t1FDh7UXOIli60XqVo-h9Pvl
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The CSS Basics course covers everything you need to get you started writing valid CSS markup to style your HTML5 pages. We will learn the syntax, major properties, and concepts such as the box model and flexbox. The end goal of this course is to write styles for our one page HTML site that we created in the HTML5 basics course.
Watch the HTML5 Basics videos:
https://www.youtube.com/playlist?list=PLMklnyuK-t1HksWhgEbehXrCmncQ9SAAw
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If you have any questions or comments, please leave them in the comments section below. I'm happy to answer them.
You can also follow me on Twitter:
@brianhaferkamp