Have been facing a weird problem for a while.
I used to try validating a page I created in WP at W3C Validator and it kept giving a 404 error, while it displayed perfectly on my blog.
Today while I was going through my error logs I realized that 404 errors were being generated for a few pages I created in WP even though I could see them.
Decided that there may be something wrong with my Permalinks and so decided to regenerate them and update the .htaccess file.
I notice that the permalinks contain the pages you create.
This means that everytime I create a Page, I will have to update my permalinks.
I do not get the 404 error anymore.