The strong element is one of a large group of elements that the HTML 4 recommendation calls phrase elements. Such elements assign structural meaning to a designated portion of the document. A strong element is one that contains text that indicates a stronger emphasis than the em element. Whereas an em element is typically rendered as italic text, a strong element is generally rendered as boldface text. Override the default with a style sheet as you see fit.

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.