Email harvesting means fetching email addresses by crawling web pages using various scripts/softwares. These email addresses then used for sending bulk marketing emails or newsletters/spams. There are lots of softwares/bots available in the market which crawls the website and gives email address from its pages. These softwares are generally known as "Harvesting Bot".
Images
Presentational Attributes vs Inline Styles
Presentational Attributes works almost like inline styles but there is striking difference between them. It is advisable to use them specifically on SVGs and IMG tags.
Show Poster Image directly from Video
Poster image is first instance on video to impress & engage user to play video. By keeping poster image clear & from video will make user interested to click on play button.
Accessible HTML5 Video Player w/ Closed Caption (CC)
To have HTML5 Video on page is good and to have it with Closed Caption is even better, as it will make video accessible for physically challenged as well.
Introduction to Javascript Promises API
A Promise is a value not necessarily known at the time of it's creation. It mainly used in asynchronous actions resulting in success or failure. The Promises represents a value which may be available now, or in the future, or never.