[SOLVED] How to design/customize the 404 error page?

Hola otra vez,

I have been looking in the documentation of SNOWFLAKE and JoomlaPlates there say, that there is a individual custom error page.
Is this the page with the big smile and the number 404? (screenshot404.jpg)
I want to design my own 404 page as I did in jp-holiday to give the user a more friendly and individually design - is this possible in SNOWFLAKE template?
(I know: "everything is possible") But I do not know where to find this 404 error answer page to customize it or to create a completely new page which answers in the case of error. Therefore I need once again your professional help.
Thanks.
Pedro de Maciot

Error page and offline can be customizes like this:
yootheme.com/themes/documentation/developers/error-pages

...but how can I have an indivudual error page as joomla article framd with the template layout? I use the ultimate template. see 2h.sen-muenchen-land.de/

As shown above:
Error page and offline can be customizes like this:
yootheme.com/themes/documentation/developers/error-pages

Problem solved.