On my Drupal 7 website, I'm getting a 404 page not found error on the front page: http://mydomain.com even though I can view the page just fine. Google Webmaster tools wouldn't validate my site; w3 website validator stops with 404 error.
I looked at my error logs in the database, and noticed that this is coming from node/1 which doesn't exist anymore. I set my home page to a different node, node/133.
This doesn't make sense to me. Either a page exists or it doesn't!