I'm trying to defer parsing i.e. GTMetrix recommendation. I tried adding this code to the end of the functions.php file:

<?php

function defer_parsing_of_js ( $url ) {

if ( FALSE === strpos( $url, '.js' ) ) return $url;

if ( strpos( $url, 'jquery.js' ) ) return $url;

return "$url' defer ";

}

add_filter( 'clean_url', 'defer_parsing_of_js', 11, 1 );

?>

but get these errors:

Warning: Cannot modify header information - headers already sent by (output started at /home2/gallag68/public_html/leadrabbit.com/wp-content/themes/salient/functions.php:7236) in/home2/gallag68/public_html/leadrabbit.com/wp-includes/option.php on line 748

Warning: Cannot modify header information - headers already sent by (output started at /home2/gallag68/public_html/leadrabbit.com/wp-content/themes/salient/functions.php:7236) in/home2/gallag68/public_html/leadrabbit.com/wp-includes/option.php on line 749

Yeah I did try that one & it made the slider invisible. Speed Booster pack did work for me though.