mememax - 3:29 pm on Dec 6, 2011 (gmt 0)

I agree with lucy, it depends on what you want to accomplish, if you want to verify if your site is delivering 404 Xenu may be a good tool to use, if you would like to discover which pages links to a 404 you can put some strings with php like:

domain.com/404?uri=URI_WHICH_GAVE_ERROR&from=REFERRER_INTERNAL_URL

this will show in your analytics as soon as someonw see it.