Blogger posts sometimes show a 404 Page not found error and this may be due to one of the following reasons
1. You have deleted your blog post2. Since you got too messy with your blog theme edit, you deleted your blog and created new blog with same name and imported your posts3. You have saved the published post as draft and republished it with a new date setting and etc
whatever reason it maybe, both people and search engines hate a “Page not found 404 error” , if there are lots of 404 errors, there is a chance that search engines de-promote your page ranking thus your traffic falls.To avoid this, you can use the custom re-direct feature present in the new updated blogger interface
1. Go to your blogger dashboard and choose your blog
2. Go to Settings -> Search Preferences -> Errors and Redirection -> Custom Redirects3. Click “Edit” -> “New redirect” and enter your old URL and new URL and click save and again save everything