What causes 404 error?

[hlbuss]

I have a new site that is 75+ pages and growing. My problem is I've already seen 77 404 error codes listed in my logs for this month.

I know a couple of basic causes of a 404 error, such as broken links and absence of a robots.txt file, but are there more? I have a robots.txt file that appears to be functioning properly.

[agerhart]

When someone attempts to access a page or file that does not exist on the site, a 404 error will come up.

[digitalghost]

Adding a favicon.ico can reduce the number of 404s.

[richlowe]

users mistyping URLs

mistyped URLs in external links

moving documents around

renaming documents

using mixed case file names on apache (unix and linux at least) without exact case match

if your purchased a used domain, it's possible that search engines and external sites have old documents indexed

nimda and other worms can cause tons of errors

RIchard Lowe

[choster]

We get more than a few hack attempts which generate 404 errors, such as users trying to access http*//www.example.net/../../../winnt/cmd.exe

(as it is a Solaris system, I imagine that these attempts are unsuccessful, but I'm just the content manager, not the security guy).

[richlowe]

http*//www.example.net/../../../winnt/cmd.exe

This is the transversal vulnerability in IIS (also was in apache some years ago although different file name to execute). Should have have been patched by all but the most lazy/least motivated/stupid administrators long ago.

Richard Lowe