Maximum PC

I can get onto this website just fine. Go through page by page but when I go to add my reply, I get the below message:

"The page you are trying to access is restricted due to a security rule.

If you believe the security rule is affecting the normal operation of your website,
you can disable it by adding the following lines to your .htaccess file:

<IfModule mod_security.c>
# Turn the filtering engine On or Off
SecFilterEngine Off
</IfModule>"

Can anyone help with this or explain why it is coming up? Thanks.

I surf the web using a proxy server so I think it has something to do with that.

Does anyone know what the above means and/or what can I do???