custom 404 1.5.6

Hi All.

I am really struggling to create a custom 404 page for my site (V1.5.6) http://www.thaimarket.com.au

Before I get flamed, I know there's a lot of threads about this already. I reckon I've read and tried them all to the best of my ability (which isn't high).

The solution link below actually worked, but created "variable undefined error" in my shopping cart when removing the last product from it, making it empty.
http://www.imagedia.com/2012/10/how-to- ... -opencart/

If any kind soul can help me with this, you'll save whats left of my hair.
Kind Regards
Daz

Solved!

For those trolling through all the "custom 404" posts. this is the one that actually works

http://forum.opencart.com/viewtopic.php?f=20&t=54975