Problem adding html to blocks
I thinks, you must twig ckeditor config file, and set config.allowedContent = true. Please, see docs http://docs.ckeditor.com/#!/guide/dev_allowed_content_rules

This links below can help you.

https://stackoverflow.com/questions/15659390/ckeditor-automatically-strips-classes-from-div

CKEDitor removes class names, even with the exception in config