How to improve speed.

Alright well I added it and it looks something like this :

<?php

/**********************************************************************************************************
 *        __   _______    _    _   _ _____ _   _ _____ __  __ _____ ____         ____ ___  __  __
 *        \ \ / / ____|  / \  | | | |_   _| | | | ____|  \/  | ____/ ___|       / ___/ _ \|  \/  |
 *         \ V /|  _|   / _ \ | |_| | | | | |_| |  _| | |\/| |  _| \___ \      | |  | | | | |\/| |
 *          | | | |___ / ___ \|  _  | | | |  _  | |___| |  | | |___ ___) |  _  | |__| |_| | |  | |
 *          |_| |_____/_/   \_\_| |_| |_| |_| |_|_____|_|  |_|_____|____/  (_)  \____\___/|_|  |_|
 *
 *				  		Premium WordPress Themes by YeahThemes.com - http://wpthms.com
 *												Copyright (c) YeahThemes
 *											http://themeforest.net/user/Manh
 *
 **********************************************************************************************************/

function _remove_script_version( $src ){
	$parts = explode( '?', $src );
	return $parts[0];
}
add_filter( 'script_loader_src', '_remove_script_version', 15, 1 );
add_filter( 'style_loader_src', '_remove_script_version', 15, 1 );

I hope that is the way its supposed to be.

Also I wanted to defer the java using this snippet

<script type="text/javascript">
function downloadJSAtOnload() {
var element = document.createElement("script");
element.src = "defer.js";
document.body.appendChild(element);
}
if (window.addEventListener)
window.addEventListener("load", downloadJSAtOnload, false);
else if (window.attachEvent)
window.attachEvent("onload", downloadJSAtOnload);
else window.onload = downloadJSAtOnload;
</script>

But I am not sure where to locate my html file to put it there.

Alright thank you 🙂 btw did I placed the code correct in custom-functions.php?