developer.mozilla.org sheds some (slightly confusing) light on that: It used to mean underline..uh rather, <u> still makes an underline but should instead be us

developer.mozilla.org sheds some (slightly confusing) light on that: It used to mean underline..uh rather, <u> still makes an underline but should instead be used for such things as squiggly lines under misspelt words – "The HTML Unarticulated Annotation Element (<u>) represents a span of inline text which should be rendered in a way that indicates that it has a non-textual annotation. This is rendered by default as a simple solid underline, but may be altered using CSS. This element used to be called the "Underline" element in older versions of HTML, and is still sometimes misused in this way. To underline text, you should instead apply a style that includes the CSS text-decoration property set to underline. ... Along with other pure styling elements, the original HTML Underline (<u>) element was deprecated in HTML 4; however, <u> was restored in HTML 5 with a new, semantic, meaning: to mark text as having some form of non-textual annotation applied. Valid use cases for the <u> element include annotating spelling errors, applying a proper name mark to denote proper names in Chinese text, and other forms of annotation. You should not use <u> to simply underline text for presentation purposes, or to denote titles of books. To underline text without implying any semantic meaning, use a <span> element with the text-decoration property set to "underline"..." https://developer.mozilla.org/en-US/docs/Web/HTML/Element/u https://developer.mozilla.org/en-US/docs/Web/HTML/Element/u