It seems you're trying to access a page that doesn't exist. I'm moderately sorry about that.
As for why you could be getting such an error, you might be looking for a file that used to exist, but no longer does (in which case, my bad), or you're looking for a file that never existed (potentially my bad).
A good deal of my previous blog posts (and portfolio items) are now lost to the ages. I used to be running a WordPress blog, but some things happened, and all of those posts are lost (if I ever find them, I'll try to port some them over here). Another good deal of blog posts have been lost to my deleting them for various reasons. If you're really keen on finding them, they should still be somewhere in the git repository holding most of the history of this site.