A form-associated element can
have a relationship with a form
element, which is called the element's
form owner. If a form-associated element is not
associated with a form
element, its form owner is said to be null.
A form-associated element is, by
default, associated with its ancestor form
element , but may have a form
attribute specified to override this.
This feature allows authors to work around the lack
of support for nested form
elements.
If a form-associated element has a
form
attribute specified, then that
attribute's value must be the ID of a form
element in the element's owner
Document
.
form
Returns the element's form owner.
Returns null if there isn't one.