Using asynchronous scripts on a webpage is the best option since asynchronous code loads more faster when compared to synchronous scripts. But it seems blogger doesn't support use of asynchronous scripts in templates, why? No one knows. Better still, there is a way you can manipulate your code to work with blogger templates.
You might have edited your blogs template several times and gotten error messages just as the one in the image below, it may be Adsense verification code, ad code or any other code that contains 'async'. Getting the problem solved is easy, just follow the instructions below.
Study the code well and look for
="async"at the front of async without spaces. Example:
Save your code. That's it. The error message will disappear immediately.
<script ="" async="async".... ></script>