The abbr element provides an encapsulation and enumeration mechanism for abbreviations that appear in the body text. For example, consider a web page that includes your company's address. At one point in the document, the abbreviation IA is used for Iowa. A spelling checker, language translation program, or speech synthesizer might choke on this abbreviation; a search engine would not include the word "Iowa" in its relevancy rating calculation. But by turning the IA text into an abbr element (and assigning a title attribute to it), you can provide a full-text equivalent that a search engine (if so equipped) can count; a text-to-speech program would read aloud the full state name instead of some guttural gibberish. Like many elements introduced in HTML 4.0, this one is intended to assist browser technologies that may not yet be implemented but could find their way into products of the future.

Netscape 6 renders the abbr element with a dotted underline, and turns the cursor into a help icon. The context menu for such an element contains a Properties choice, which leads to a displayed list of attributes and their values for the visitor.

A related element, acronym, offers the same services for words that are acronyms (although Netscape 6 offers no special rendering). Both elements are part of a larger group of what the HTML 4.0 recommendation calls phrase elements.

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.

An advisory description of the element. For HTML elements that produce visible content on the page, IE 4 and later and Netscape 6 render the content of the title attribute as a tooltip when the cursor rests on the element for a moment. For example, the table-related col element does not display content, so its title attribute is merely advisory. To generate tooltips in tables, assign title attributes to elements such as table, tr, th, or td.

The font and color properties of the tooltip are governed by the browser, and are not modifiable under script control. In IE/Windows, the tooltip is the standard small, light-yellow rectangle; in IE/Mac, the tooltip displays as a cartoon bubble in the manner of the Mac OS bubble help system. Netscape 6 tooltips are the same small rectangle on all OS versions. If no attribute is specified, the tooltip does not display.

You can assign any descriptive text you like to this attribute. Not everyone will see it, however, so do not put mission-critical information here. Browsers designed to meet web accessibility criteria might use this attribute's information to read information about a link or nontext elements to vision-impaired web surfers. Therefore, don't ignore this potentially helpful aid to describing an element's purpose on the page.

Although the compatibility listing for this attribute dates the attribute back to Internet Explorer 3 and HTML 3.2, it is newly ascribed to many elements starting with IE 4 and HTML 4.0.