HTML5 is not yet fully functional in all browsers and much of your audience will be unable to view some of the code; generally speaking 75-90% of your subscriber list. Whenever using HTML5 mark-up, be sure to create an appropriate alternative so that users can still get information if they are not able to view the video.
Video Email Auto-play with Sound
Whilst video email is a great way to communicate with your subscriber list, it has been shown that videos that auto-play with sound increase the complaint rate. If you are going to use video email when messaging your list, by all means code in auto-play. However, be sure to have the video on mute and give your viewers an option to turn on the sound. This is also true for websites in general and auto play with sound is an internet marketer’s nightmare.
Fail-overs for non-HTML5 users
A ‘fail-over’ is a piece of code that will replace the previous code if it is not viewable in a browser. This means that you can be certain that your entire audience will be able to view content in your e-mail. Creating fail-overs requires some advanced coding knowledge, but there are many sites that offer an alternative visual for viewers who are using non-compatible HTML5 browsers. This can have your video replaced by text or even a gif image that allows the user to view (and click) an animated advert. Whilst nowhere near as powerful as a video, having a fail-over can dramatically increase your conversion rate for those who use browsers that do not support HTML5.