Place this file in the application/core directory of your CodeIgniter project and you will find comments in your HTML at the start and end of every view.

MY_Loader.php

<?php defined('BASEPATH') || exit('No direct script access allowed');
/*
Override CI loader to add comments indicating the location and count of views as they are loaded.
Copyright (C) 2012  Ryan Neufeld

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

*/

/**
 * Custom extension of the CI_Loader class to provide convenience methods for developers.
 *
 * @author Ryan Neufeld <ryan@neucode.org>
 * 
 */
class MY_Loader extends CI_Loader
{
	/**
	 * List of views and a counter for every time one is loaded.
	 *
	 * @var array
	 */
	public $views = array();

	/**
	 * Override CI's view loader.
	 *
	 * @param  string  $view   The view name to load.
	 * @param  array   $vars   View variables.
	 * @param  boolean $return Return a string (true) or just load the view.
	 *
	 * @return mixed
	 */
	public function view( $view, $vars = array(), $return = FALSE )
	{
		// Skip adding comments to views loaded outside development environment.
		if (ENVIRONMENT !== "development")
		{
			return parent::view( $view, $vars, $return );
		}

		// Keep track of number of times a view is loaded.
		if (!isset($this->views[$view]))
		{
			$this->views[$view] = 0;
		}

		$this->views[$view]++;


		if ($return)
		{
			$result = parent::view( $view, $vars, $return );

			return "<!-- start " . APPPATH . "views/$view ({$this->views[$view]}) -->\n{$result}<!-- end " . APPPATH . "views/$view ({$this->views[$view]}) -->\n";
		}

		echo "<!-- start " . APPPATH . "views/$view ({$this->views[$view]}) -->\n";
		echo parent::view( $view, $vars, TRUE);
		echo "\n<!-- end " . APPPATH . "views/$view ({$this->views[$view]}) -->\n";
	}
}