Tuesday, August 12, 2008 at 2:54 PMWe see two kinds of 404 ("File not found") responses on the web: "hard 404s" and "soft 404s." We discourage the use of so-called "soft 404s" because they can be a confusing experience for users and search engines. Instead of returning a 404 response code for a non-existent URL, websites that serve "soft 404s" return a 200 response code. The content of the 200 response is often the homepage of the site, or an error page.
How does a soft 404 look to the user? Here's a mockup of a soft 404: This site returns a 200 response code and the site's homepage for URLs that don't exist.
As exemplified above, soft 404s are confusing for users, and furthermore search engines may spend much of their time crawling and indexing non-existent, often duplicative URLs on your site. This can negatively impact your site's crawl coverage—because of the time Googlebot spends on non-existent pages, your unique URLs may not be discovered as quickly or visited as frequently.
What should you do instead of returning a soft 404?
It's much better to return a 404 response code and clearly explain to users that the file wasn't found. This makes search engines and many users happy.
Can your webserver return 404, but send a helpful "Not found" message to the user?
Of course! More info as "404 week" continues!