All kinds of server/software problems that may be caused by security issues, for example
- website is suspended
- web pages report PHP or database errors
- webpages want load because of server error
While such issues may have their origin in pure techical problems unrelated to hacker attacks, it's still a good idea to notify webmasters about them, since it's a sign that website does not work properly (or won't load completely) and this issue should be resolved as soon as possible anyway.
Affecting: Any web site (no specific target).