The u element renders its content as underlined text. This element is deprecated in HTML 4 in favor of the text-decoration:underline style sheet attribute. The element does not validate in strict HTML 4 or XHTML DTDs, and may confuse users who regard any underlined text as a clickable link, regardless of color.

The language being used for the element's attribute values and content. A browser can use this information to assist in proper rendering of content with respect to details such as treatment of ligatures (when supported by a particular font or required by a written language), quotation marks, and hyphenation. Other applications and search engines might use this information to aid the selection of spell-checking dictionaries and the creation of indices.