problem about 404 page

I know how to create a custom 404 page.The problem is I don't know how to get it worked.
Ok,if I type a wrong url (like: http://nizhongmin.co.uk/abc )
It gives me a 500 page,how could I set it a 404 page when someone types a wrong url?
Thanks for the help,
Richie

 

surly it's problem with htaccess ??

can you give the source of .htaccess file so i could know more about your problem ?

 

Here's the simple code:

DirectoryIndex index.html
ErrorDocument 404 /missing.html

Code (markup):

I'd like to let others see the 404 page when someone types a wrong url,but it shows a 500 page instead.