404

I have the 404 template supplied however it is not triggered into being used when there’s a 404 error.
I’ve looked at the 404 template .php files … I assume that if the supplied 404 is not being triggerd then this is where I edit the 404?
Consequently – not use the supplied (and adapted) 404.

…Could you tell me, if I’m to use the .php file where exactly within the code I should input the html or any pitfalls I may encounter

Also – the .php file defaults to using the slider – I don’t want this how do I take the slider out of the 404 page .. thanks.

Alternatively tell me how to trigger the 404 page that I’ve created as a “page” …
Thanks