# File TagTreeScanner.rb, line 494
                def replace_child( old_child, new_child )
                        if ( prev = old_child.previous_sibling ) == new_child || old_child.next_sibling == new_child
                                remove_child( old_child )
                        else
                                new_child.parent_tag.remove_child( new_child ) if new_child.parent_tag
                                remove_child( old_child )
                                insert_after( new_child, prev )
                        end
                        old_child
                end