The best 404 page I ever created had a large button in the middle of the (branded) screen that said "report". Which dispatched an email to me with relevant information (referring url etc.)
I know this could have been done automatically with some scripting, but having it manual meant only 'real' users would be reporting 404's (not bots etc.) and I found users reported the 404's rather than just moving on.
You don't want your 404 to be too helpful, it's something that should be fixed (if at all possible)
> You don't want your 404 to be too helpful, it's something that should be fixed (if at all possible)
Sure you do - It's not just a bad link that could cause a 404. Could be an old bookmark, a bad link from another site, a bad cut'n'paste, a link to deleted content, or whole bunch of other things.
A useful 404 would do things things like (1) search for content based on your url and give suggesttions and (2) allow you to conduct a search... and (3) well, probably all the other things in the article.
The best 404 page helps the user find what they were looking for. You can run a cron job on your server logs to analyze your log files for statistically significant problems (not just 404's); that script can report them all to you my email or SMS or whatever. Further, you can run cron jobs that crawl your site looking for broken links, and/or replay some of the previously-working GET requests; then you will find broken links even when nobody is using your site.
I know this could have been done automatically with some scripting, but having it manual meant only 'real' users would be reporting 404's (not bots etc.) and I found users reported the 404's rather than just moving on.
You don't want your 404 to be too helpful, it's something that should be fixed (if at all possible)