Underlines text inline.
Deprecated in HTML4, redefined in HTML5. In HTML5 it is used to express “an unarticulated, though explicitly rendered, non-textual annotation,” such as a proper name in Chinese or a spelling error.
This example uses the u element to identify a word in a sentence, without any particular semantics.
We would like to call your attention to the second "the" in "The quick brown fox jumped over <u>the</u> lazy dog."
Microsoft Developer Network: [Windows Internet Explorer API reference Article]