Template:Flexbox-item-header

Flexbox-item-header opens a wrapper for elements within a flexbox.

It sets several CSS properties that are meaningless outside of an HTML element with.

It must be closed with either Template:Flexbox-footer, or a.

Flexbox-item-header accepts two parameters. is required and sets the position of this flexbox-item relative to others; it accepts any integer. allows for arbitrary CSS.

Frankly, the code for this is a mess, but it is necessary until the underlying technology is a more widespread web standard.