I recently noticed that google are keeping indexing my non-existed pages of my website which I change the names of them several weeks ago. I customized 404 page with 404 in HTTP header too. But it seems not working effectively. Can someone tell me how to stop google indexing my non-existed web pages?
These pages have been linked by somewhere before you changes the name of them so thats why Google crawler can still read them. Go to webmaster tools and check your 404 error pages and from where they are linked.
you can block them by a robots.txt and delete them from google webmaster tools. and you can redirect them to homepage by 301 redirect.