odd placement on my widget

I have just joined the world of programming widgets, and im obviously not that good because i made a sidebar widget to display authors and it only displays in the furthest top left corner of my page.

Can anyone point out whats wrong in my code.

add_action('widgets_init', 'widget_display_author_init');
function widget_display_author_init() {
  	if ( !function_exists('register_sidebar_widget') ) {
  		return;
	}
  	function widget_display_author($args) {
  		extract($args);
  		echo "$before_widget<div id='display_author'></div>$after_widget";
	}
  	register_sidebar_widget('Display Author', 'widget_display_author');
}

add_action('wp_head', 'display_author_wp_head');
function display_author_wp_head() {

	wp_list_authors();

}

Thanks!