When an HTML element or attribute is rendered obsolete by newer web technologies, it will remain possible to use it for some time. However, the W3C recommends that you do not use these obsolete elements: they are deprecated. For example, the <u> element was used to underline text. However, the visual appearance of text is now better handled using CSS, in this case the property "text-decoration" (which can be set to "underline"). The <u> still works; but it is no longer the best method, and may eventually stop working.