Top 'page not found' errors

this is quite easy in webmaster tools. go to 'Links' > 'Pages with external links' and open the 'Find a page' fieldset. enter the url, click on see details. on the right there is the number of external links to that page. click on that number to display the external URLs pointing that 'page not found' page.

edit: the same feature exists for the 'Pages with internal links'. This is probably more relevant here i.e. it will give all the drupal.org pages containing broken links to drupal.org.

@scor - Google webmaster tools are useful yes.
On page not found for us, we have 29 pages but the vast majority are broken/dead links to spammer accounts.

On the other... well, that's an interesting process but seems to be a manual per page process and webmasters tools shows, well.... first page 1 to 30 of 15987

I believe what Amazon is looking for is more in the nature of automation to determine live/dead links and report on them without bringing our database to it's knees.

Well there's this: http://validator.w3.org/docs/checklink.html

Never used the non-web version but it's supposed to be able to handle large sites without putting too much load on.

alternatively, there is also the ubuntu linkchecker package written in python.

After more than one year, or this task has been done, or it will never be done.
I am closing this report.