The horizontal line below should not be red. It should be green with (optionally) a thin red border.

Expected result (screenshot):

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"Essentially, IE treats them [horizontal lines] as inline elements, while the others [browsers] treats them [horizontal lines] as block elements." coming from How do I style an hr?
<hr> is a block-level element, not an inline-element.

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The correct answer should be, must be block, not inline.

Valid HTML 4.01! CSS compliant