heh ... ok here's were a server admin steps in:
ErrorDocument should only be used if your sending the bad hit back to your own server and then you use the path to the file.
Example:
ErrorDocument 404 /home/userid/domain.coc/htdocs/index.html
If you are sending the bad hit off your server to another server then you need to use ReDirect.
Example:
Redirect 404
http://someothersite.com
By using ErrorDocument 404
http://somesite.com you are creating a load on the machine. If you have enough power in your server you may not notice this but your apache error logs will suffer.
Peace,
JFPDude