<warning> text <\warning>
The text of the warning message is printed in boldface.
The default heading for the warning is "Warning". To specify a different heading, use the <head> element.
To display a graphic with the warning, define WarningElementDefaultIconFile in an <!entity> declaration. The default warning icon named warnicon.pm is located in the /usr/dt/dthelp/dthelptag/icons directory.
The <\warning> end tag is required.