http_url_validation_improved

https://github.com/kete/http_url_validation_improved

a Rails gem that allows you to validate a URL entered in a form. It validates if the URL exists by hitting it with a HEAD request. The improved version includes retries for common patterns when the head request is refused before giving a failure notice. It also looks up a SITE_URL constant to the user agent in the headers. Also has the option to also check that the URL returns content of a specified type.