The Java EE 5 Tutorial  Including Directives in a JSP Document
Directives are elements that relay messages to the JSP container
and affect how it compiles the JSP page. The directives
themselves do not appear in the XML output.  There are three
directives: include, page, and taglib. The taglib directive is
covered in the preceding section.  The jsp:directive.page
element defines a number of page-dependent properties and
communicates these to the JSP container. This element must be a
child of the root element. Its syntax is  <jsp:directive.page
page-directive-attr-list />  The page-directive-attr-list is the
same list of attributes that the <@ page ...> directive has.
These are described in Chapter 5, JavaServer Pages Technology.
All the attributes are optional. Except for the import and
pageEncoding attributes, there can be only one instance of each
attribute in an element, but an element can contain more than
one attribute.  An example of a page directive is one that tells
the JSP container to load an error