Google’s Page Speed test recommends the we leverage browser caching. To do this in Windows using IIS, open the site’s web.config and add a client caching directive:
<system.webServer>
<staticContent>
<clientCache cacheControlMode=”UseMaxAge” cacheControlMaxAge=”365.00:00:00″/>
</staticContent>
</system.webServer>
**There are “per file” rules that can be applied but this seems to be sufficient for Google
Pasting this here for future reference (from an email generated by WPMU Dev):
Site speed isn’t all about images though – there are heaps of other things to look at, too. I’ve collected a few posts from our blog that nicely sum up what you should look at to get your site operating at 100% optimal speed.
Here’s a quick overview of five areas to work on
This one is a comparison of a few top caching plugins (WP Super Cache, W3 Total Cache and WP Rocket)
A simple list of the 10 fastest WordPress themes
You like image optimization, so here’s some more detail about that
This is a big 22 step outline of every aspect of optimizing speed on your wordpress site
And finally, an in-depth drill-down on how we managed to get a WordPress site to a 91/100 on Google Pagespeed Insights
From: http://www.sitepoint.com/ten-quick-fixes-reduce-page-weight/?utm_source=dlvr.it&utm_medium=facebook
You may need to use tools such as Chrome’s Audit Developer Tool, JSLint, Dust-Me Selectors, CSS Usage, unused-css.com or build tools such as grunt-uncss.