
Explanation/Reference:
* -ms-flexbox
To enable flexbox layout, you must first create a flexbox container. Do this by setting the display property of an element to either "-ms-flexbox" (for a block-level flexbox container) or "-ms-inline-flexbox" (for an inline flexbox container).
* -ms-flex-direction: row;
When creating a flexbox container, you can also set its orientation-that is, specify whether its children are displayed from right-to-left, left-to-right, top-to-bottom, or bottom-to-top.
* -ms-flex
Specifies whether the width or height of a child element is flexible based on the space available in the object. This value also indicates the proportion of space available that is allocated to the child element.
Reference: Flexible box ("Flexbox") layout in Internet Explorer 10