Created the module for Blocks but the block is not listed

This is my first module to write. It is suppose to create a block for a Yahoo ranking list.

I thought that this code and using Hook_block() will make this block show up within the Block Setup List Page. However, it is not.

I am not an expert in the code, but I am trying to find my way around within all the Jumboo-Mumboo :)

Please let me know what I am missing. If I would like to add more code from Yahoo, where should I insert this code.

<?php
// $Id$

/**
* @file
* Implements various blocks Blocks for listing yahoo rank..
*/

/**
* Implementation of hook_block().
*/
function approval_block($op = 'list' , $delta = 0, $edit = array()) {
switch ($op) {
case 'list':
$blocks[0]['info'] = t('Yahoo Rank');
$blocks[0]['cache'] = BLOCK_NO_CACHE;
return $blocks;
}
}

Thank you for your help.