Just copy paste the following following lines to your function.php file.

function add_favicon() { ?>
<link rel=”shortcut icon” href=”<?php echo bloginfo(‘stylesheet_directory’) ?>/images/favicon.ico” >
<?php }
add_action(‘wp_head’, ‘add_favicon’);

if wp_head() function added in your header.php file, If that function not added then this hack will never work

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