I started to creating a blog to browse-tutorials.com. I used to have a blog in blogspot where I did post some interesting content, but it was mostly references. I decided to put more effort in blogging and now I have blog here. I created a new ad block to the footer of my blog. I noticed that asynchronous code was the default option. So asynchronous ad code is out of beta.
I saw some more unusual html tags/attributes and started to wonder if it works in all browsers etc. Also I was confident that Google wouldn't have made it recommended without it being tested hard. So I decided to take a look into it.
The advantage of asynchronous code is that it never gets in the way of other parts of your web page loading. It is reducing the latency especially for mobile users.
I didn't find any material about the asynchronous google adsense code not working in some browsers.