Recently, this blog has encountered 412 Precondition Failed error that made it not possible for some users to access the site as some visitors are considered as spammer. After several check, the issue was solved by disable Bad Behavior plug-in. After the removal of the plug-in, the blog pages also served much faster.

Precondition Failed

We’re sorry, but we could not fulfill your request for / on this server.

We have established rules for access to this server, and any person or robot that violates these rules will be unable to access this site.
To resolve this problem, please try the following steps:

1) Ensure that your computer is free of viruses, Trojan horses, spyware or any other sort of malicious software.
2) If you are using any sort of personal firewall or browser privacy software, check to ensure that its settings do not cause your web browser to inadvertently violate any of the rules listed below.
3) Disable any download accelerators you may be using. They don’t speed up your downloads anyway; in most cases, they actually run slower!
4) If all else fails, try using a different Web browser, such as Firefox.

More Information

For your reference, the conditions for access to this server are:

Robots:
MUST read and obey robots.txt.
MUST identify themselves properly; for example MUST NOT identify as Mozilla.
MUST NOT pretend to be a human.

Humans:
MUST NOT pretend to be a robot.
MUST NOT use a computer infected with viruses, Trojan horses or other malicious software.

Both:
MUST NOT harvest email addresses.
MUST NOT attempt to send spam.
MUST NOT attempt to compromise server security.
MUST NOT use excessive amounts of bandwidth or other server resources.

The precondition on the request for the URL / evaluated to false.