Changes in HTML 5 - <u> Tag

The <u> tag was deprecated in HTML 4 and considered invalid in later versions, but has now been added back into the WHATWG HTML Living Standard and W3C HTML 5 (after the two versions diverged - see difference between HTML 5 and HTML Living Standard). Therefore, whether or not the u element is valid depends on the version of HTML:

• HTML 2 and earlier - <u> tag did not exist
• HTML 3.2 - <u> tag added
• HTML 4 - <u> tag deprecated, invalid in HTML 4 strict DTD
• XHTML - <u> tag invalid
• WHATWG HTML 5 - u element invalid
• WHATWG HTML Living Standard - u element added
• W3C HTML 5 - u element added