Here is something i use when developing themes:
add_filter( 'template_include', 'store_template_file', 999 );
function store_template_file( $template ){
$GLOBALS['current_theme_file'] = basename($template);
return $template;
}
add_action('wp_footer','print_theme_file');
function print_theme_file(){
if( !isset( $GLOBALS['current_theme_file'] ) || is_admin() )
return;
echo '<!-- Current theme file: ' . $GLOBALS['current_theme_file'] . '-->';
}
Once you paste that in your theme’s functions.php file it will print out an HTML comment at the footer with the theme file’s name.