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The problem I'm having is when I check the cache of a recent post (around 6 days old) I get the Google 404 error pageHow do you check for cache? Do you mean you have clicked a "Cached" link in Google SERPs or are you using one of toolbars or similar?
But that still doesn't explain what google-- of all people!-- is doing, linking to a page that doesn't exist. Do they create the URL for the cache before creating the cache itself?From what I could see there are (at least) two different ways Google URL for cache can be constructed as. Both have q=cache: with the domain name, but the "Cached" link from the serps has additional parameters such as SERPs keywords, position of listing within the SERPs, language, google geolocation, and a nnnnn string that probably tells google something as omitting it still returns the same result. This link would highlight the search string on the cached page. URL q parameter example:
I have seen CMS site pages get cached right after creation but the author was creating the page for a story that wasn't finished, the CMS doesn't actually have a rewrite assigned to the content and somehow crawlers see it, try to hit the page and get a 404.