The outputclass attribute

When you need an element to appear differently in the output from other elements with the same semantics, you can provide a value in the element's outputclass attribute.

Most block and phrase elements in DITA have an outputclass attribute. This attribute is used to provide output styling information, when necessary.

When published to an HTML-based output format, the value in the outputclass attribute of an element will be passed through to the CSS class attribute in the HTML code.

You should avoid using the outputclass attribute, as it is not a semantic marker. The presentation of the output should be determined by the publishing tool automatically converting semantic mark-up to formatting rules.