I think we need to define his question further. I read it as if he goes to a website, and the website itself doesnt exist, how can he change the error message that Internet explorer returns back to him. Not what happens when you got a website and the page is not found and you get a 4XX error.

Also saying that this all has to do with .htaccess is very misleading as you will only use .htaccess for user level webpages, not system wide web pages. Using .htaccess is actually much more system intensive than using httpd.conf for making these changes.

If you are talking about how to change the error messages that are sent by the webserver itself then the following is what you need.

For apache, if you want to change the error messages system wide returned to you for the various error messages, you would change that in the httpd.conf. Under most linux distrubutions, this file is found in /etc/httpd.conf. If you are referring to a user level website, then you can use .htaccess for this.

For IIS, you will change the web page that is returned by using the Internet Information Services Manager, open up the website properties or the WWW properties and changing the document that is returned for the various web pages

If you are referring to the error message that Internet Explorer returns when you go to a nonexistant domain, like http://www.asdafassdasd.com/, then it is probably hardcoded into some .dll that internet explorer uses. I would be curious to know what file has these messages myself.

Hope this helps.

Grinler