Corrected two typos

"don't" with &apos; should be more correct than &rsquot; (or is it better to escape it \' ?)
I personally find the line * translators: %1$s: smiley */ pretty confusing, but at least it should be singular (not smilies)
Merge pull request #84 from pixolin/patch-1

_s: Correct two minor typos in 404.php.