This may sound funny but it would be great if the wording in the Genesis 404.php could be changed to read differently. As it is, it is overly verbose and really doesn't use proper grammar. This is how it reads now:
"The page you are looking for no longer exists. Perhaps you can return back to the homepage and see if you can find what you are looking for. Or, you can try finding it by using the search form below."
I have bolded the questionable grammar. Some of the 404 pages I have seen are quite friendly, saying something like what is found in the WP Codex page for creating a 404 page.
Anyway it is just a thought. I made some CSS changes to the default 404 page on my site but can't change the verbiage.