Updates to plain HTML aren't as exciting as say, your scripting / server-side language of choice, but seeing as it's the backbone of the front-facing web, it's a good idea to check-up on old faithful every so often. If you've decided to choose today to pop in -- great timing! HTML 5.1 recently became World Wide Web Consortium's "gold standard".
If you want the full details, you can read the W3C's official blog post on HTML 5.1 from November. Alternatively, if you just want a summary of notable changes, RankRed has you covered with a breakdown of 14 important additions.
Interestingly, the first thing RankRed points out is the standardisation of
rel="noopener" for hyperlinks that use the
target="blank" attribute, something we brought up mid-last year:
In order to completely eliminate this issue, HTML 5.1 has standardized the usage of the rel=”noopener” attribute which separates browser contexts. The rel=”noopener” can be used within <a> and <area> tags.
Many of the other inclusions to the standard are, unsurprisingly, features web developers have been using for years. However, by making them official, it'll encourage browser vendors to support them fully (and hopefully, consistently). For that reason, the RankRed article is worth a read in its entirety.