HTML defines a series of six heading levels with associated numbers that are intended to signify the relative importance of the section below the heading. The h1 element represents the most important, whereas h6 represents the least important. HTML document parsers can examine a page's tags to create a table of contents based on the headings. This means that for proper document structure, these heading levels should be used in sequence, without skipping levels for aesthetic purposes.

It is up to the browsers to determine the default font, weight, and other characteristics of each level. Each heading element is rendered on its own line, with no line break or paragraph elements necessary to begin the content of the section titled with the heading. Figure 8-3 shows examples of how Netscape 6 and Internet Explorer 6 renders all six heading levels in Windows. By and large, this pattern applies to other browser versions and operating systems.

You can always override the browser's rendering style for any heading level or individual heading with style sheet rules.

Determines how the element's text is aligned inside the element's block. Both Navigator and Internet Explorer support alignment values for center, left, and right alignment. Transitional HTML 4 (but not XHTML) adds the possibility of a fully justified alignment for multilined content, as well.

The align attribute is deprecated in HTML 4 in favor of the text-align: style sheet attribute.

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.