Begginer ask

[eluser]Kentus[/eluser]
Ok, i'm new in this domain, and i want in this topic to expose my problems that i'll receive for this framework.

I buy a domain: http://earth-war.eu/ and i tried to make the samples from video tutorials where i'll learn to make my own blog.

For the first video i've received some errors:
first said that:
Fatal error: Class 'Controller' not found in /home2/earthwar/public_html/Blog/application/controllers/blog.php on line 3

for the next code:
<?php

class Blog extends Controller{

function index()
{
echo'Hello World'
}

}

?>

I replaced Controller() with CI_Controller and worked, but when i tried to create the constructor i received this:

Fatal error: Call to undefined method CI_Controller::CI_Controller() in /home2/earthwar/public_html/Blog/application/controllers/blog.php on line 7

I replaced with Controller but same error undefined method CI_Controller::Controler().
The code:
<?php

class Blog extends CI_Controller{

function Blog()
{
parent::CI_Controller();
}
function index()
{
$data['title']="My Blog Title";
$data['heading']="My Blog Heading";
$data['todo']=array('Clean house','eat lunch','call mom');
$this->load->view('blog_view',$data);
}

}

?>

Please help i'm a little stuck on this error and i don't know what to do.
Thanks a lot for future help.
One more thing.. if you see errors in my grammar or my exprimation pls correct me if you have time). Thanks again