As WordPress gets more sophisticated and WordPress Themes become more interesting, powerful and complex, the code itself begins to bog down. One of the better ways to troubleshoot this issues is by using Google Developers PageSpeed Insights.
I just had to do some research on a photographer’s WordPress site to attempt to fix some of these problems. Here are some links to plugins that will help in this process.
W3 Total Cache
WP Performance Score Booster
WP Super Cache plugin
Some free CDNs use available caching plugins such as WP Super Cache.
Photon by Jetpack
Validator.nu Living Validator
W3C Validator Service