This month Google Webmaster Tools updated its list of crawl errors to include Soft 404s. What is a Soft 404? Basically it indicates a missing page that is getting referenced (via an internal or external link) and followed by the search engine spider. Usually a server setting redirects traffic to the missing page address to a designated page, or the homepage. For instance, someone coming to your site from a bad link would normally see an ugly 404 page (or whatever the browser serves up) but a quick setting in your website server can show people a small sitemap or the homepage. This can be good for the user experience but bad for search engines.
The solution for Soft 404 errors involves identifying the pages that show these errors and making one of the two following repairs. First, see if you have any internal links referencing a page that is no longer there, or a page that has an error in the link address. Second, you can 301 redirect any unfixable links to the appropriate pages, or to the homepage. A link may be hard to fix if it is on someone else’s website, or there may be multiple instances of the link out on the web.
Fixing Soft 404 Errors (also called “Crypto 404s”) may be very beneficial to your link popularity. When a server chooses to redirect people to a default page from a 404, PageRank isn’t being passed, and Google obviously is seeing a page that isn’t there, which therefore contains no content. Whether you get a physical link to go to the right location, or 301 redirect “missing” links to the homepage, you are helping Google tighten up its index, and focusing links where they belong. No matter how Google is finding the Soft 404s, it makes sense to take this issue off their radar so your site content gets the consideration it deserves.