Error parsing XML, line 666, column 112 The entity name must immediately follow the '&' in the entity reference.

Error parsing XML, line 666, column 112 The entity name must immediately follow the '&' in the entity reference.

While editing the blogger template html, I faced the below error.

Error parsing XML, line , column  The entity name must immediately follow the '&' in the entity reference.

This occurs because you have character "&" in the html code. which you need to replace it with "&"
This has solved my issue and I was able to save the html