id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
12641	Move comment-reply to the bottom of the page	josephscott		"The general rule for browser performance is to load JavaScript as late in the page as possible.  The TwentyTen theme makes use of the comment-reply JavaScript code that comes with WordPress, and includes in the header.  From what I can tell there's no need to include it in the header, since it deals with the comment reply form, generally at the bottom of the page.

So I did some tests.  I removed the

{{{ <?php if ( is_singular() ) wp_enqueue_script( 'comment-reply' ); ?> }}}

in header.php and replaced it with 

{{{ <?php if ( is_singular() ) wp_print_scripts( 'comment-reply' ); ?> }}}

at the very bottom of footer.php, just after the wp_footer() call and before the closing BODY and HTML tags.  The idea being to allow browsers to load the comment-reply JS as late as possible.

I then used webpagetest.org to run load tests (IE8).  Here's the waterfall chart before my changes - http://www.webpagetest.org/result/100318_63M1/1/details/ - and after my changes - http://www.webpagetest.org/result/100318_63M3/1/details/

You'll notice that the after chart has more parallel downloads of page resources.  Specifically in the before chart all other downloads are blocking until it finished getting comment-reply.js.

I also looked at the charts in Chrome (resource inspector) and Firefox (firebug), both show similar results, with more parallel downloads happening with comment-reply JS moved to footer.php.

I haven't seen any downsides to this move so far.  If this breaks something or causes other problems let's see what we can do to deal with them.  In the mean time I'm including a simple patch to make this change.
"	enhancement	new	normal	Future Release	Performance	3.0	normal		has-patch	joseph@… mt@…