How to detect web site design changes

I am working on web scrapping using python and mostly i found that crawler is not able to crawl the website because web site structure/design (tag name of css class name) is changed. Once website design changes then i have to change my code every time. There are many ways using machine learning to check content is updated or not. But i haven't found any clue on web structure change detection mechanism.

My question- Is there is way to detect design or structure related changes in web page. May be using machine learning stuff or any research paper around it.

Please help if there is any resource available.