Go ahead and take a look at the design of this 404 page; as you can see it is very clear. I have specifically chosen something so simple and clear so that we don’t get lost in the unnecessary bells and whistles.
The overall look and feel of this design is simple for the sake of the example; at the same time so is the layout. As I will explain to you shortly, a 404 page shouldn’t have a lot going on, so the layout is kept simple too. You don’t need clutter in any of your pages, including the error ones.