On April 23rd, a webmaster went to the Google Webmaster Help forums because his site’s home page was not being fully indexed and kept on dropping out of the index. The question really baffled a lot of SEOs, some had some guidance but none of that guidance really seemed to have worked.
John Mueller of Google even came in on May 2nd and offered some advice around something is preventing GoogleBot from indexing the site. He wrote:
A lot of times when we try to crawl & render your pages, we see a 404 page instead of the actual content. That’s why we’re dropping those pages afterwards. Off-hand, I don’t see anything specific that would be causing this, but is it possible that your site responds in that way if individual resources used on the page can’t be fully loaded?
Then, this morning, John Mueller said “yep, we spotted & fixed some things on our side there.” It sounds like Google made a change on the Google end to index the site properly. Maybe Google fixed a weird edge case indexing bug?
So sometimes it pays to post your issues in the Google forums – sometimes.
Forum discussion at Google Webmaster Help.