In most cases that I've encountered something similar, I have attributed it to either:
Referrer spam - www.domain.com is hitting your site in the hopes that the webmaster is reviewing incoming links. This is more likely the case if you have a non-404 response where the referrer may be published somewhere.
Vulnerability scans - Every day I encounter a huge number of scans over my site seeking out applications with known vulnerabilities. Due to the automated nature, most will result in 404 (particularly if you use a little "security through obscurity" and avoid common install directories). Generally, a search for the 404 page name (eg. /webcams/935.html) would reveal other public installs of this app, but it doesn't appear to be the case here.
Bad linking - Somewhere this deep link was posted incorrectly. Perhaps you could try using Google's "link:" to see if you can locate an instance of this link.
With the details you've provided (the fact that it's a 404 and the fact that the /webcams/935.html isn't a commonly known public app link), I'm less convinced that these are the likely reasons.