Invalid HTML doesn’t affect your site’s SEO value. However, valid HTML is considered best practice, and with a good reason.
2.8.1 – Integral Adroitness
This update fixes a corner case bug regarding PHP mbstring. If you haven’t read the 2.8.0 upgrade notes yet, please do.
2.8.0 – Ventricular Perspicacity
This major release not only fixes various bugs, but also introduces new options for you to fiddle with.
You’re now able to adjust General Settings easily! These settings include options to adjust the cache, (re)move the SEO Bar, and set a Canonical Scheme.
Google’s Knowledge Graph has been transformed into something much bigger last year, so the related settings now fall under a new name: “Authorized Presence”.
You can now select your website’s social images. With this much asked for feature, you’re now really in control.
You can now also control the style of your sitemap. The sitemap title will link back to your homepage when clicked upon.
SEO Tip: Following visitors, hook them with an introduction
If the visitor is hooked, the visitor will stay on your page and will read on or click through your website.
2.7.3 – Incandescently Binate
This update makes sure no conflicts arise anymore with WP Engine’s staging services when WordPress is at a major version release.