[title]ModSecurity[/title]

You may have just been impacted by ModSecurity, which is an unofficial web server plugin that many webhosts install.
It interferes with request patterns it thinks are "suspicious", which can block normal form posts, such as when saving customised HTML in the Admin Zone.

Unfortunately there is no standardised workaround we can deploy for you. You will need to ask your webhost to disable ModSecurity, or at least disable troublesome rules in it.

[url="More information is available"]http://compo.sr/docs/sup_modsecurity.htm[/url]
