Who: Technical Users What: The Views 404 module returns 404 codes when you enter in any thing in the URL after your defined view URL. When: Use this module when your website is showing a lot of duplicate content in the search engines from your Views. Note: DO NOT USE THIS MODULE IF YOU HAVE VIEWS WITH URL BASED ARGUMENTS! Where: This module is an oddity, I couldn't find any configurable options at all. Just enable it and for get it. Why: This module is for people who want to get every bit of SEO into a site. I don't use this module and I've never run into too much of an issue with duplicate content.