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Yeah definitely it affects ranking and also our time.
Yes, is the answer and definetely if you have it in large numbers.
Let me quote Google from the Webmaster Blog :
"We discourage the use of so-called "soft404s" because they can be a confusing experience for users and search engines. Instead of returning a404 response code for a non-existent URL, websites that serve "soft404s" return a200 response code. The content of the200 response is often the homepage of the site, or an error page."
Source : Google Webmaster Blog on Soft404
