A fieldset element is a structural container for form elements (as distinguished from the functional containment of the form element). In fact, you can define multiple fieldset elements within a single form element to supply context to logical groupings of form elements. For example, one fieldset element might contain text input fields for name and address info; another fieldset might be dedicated to credit card information.

Supporting browsers boost the attractiveness of this element by automatically drawing a rule around the form elements within each fieldset container. You can also attach a label that gets embedded within the rule by defining a legend element immediately after the start tag of a fieldset element. By default, the box extends the full width of the next outermost container geographyusually the document body or html element. If you'd rather have the box cinch up around the visible form elements, you have to set the width style sheet property for the element.

The align attribute appears only in Internet Explorer, and its implementation is far from consistent across operating systems. In theory, the attribute should control the alignment of input elements it contains. This is true in the Macintosh version of IE, but in the Windows version (especially in IE 6), the settings have minor effect on the fieldset element rule. It is best to let the default setting take precedence, and override with style sheets.

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.