A few months ago Mads posted some IIS URL Rewrite rules in a post titled “URL rewrite and the www subdomain”. Years ago, when I rewrote this site in ASP.NET MVC, I found URL rewriting to be invaluable. Some URLs in the new version of this site became obsolete. For example, an efficient Gravatar implementation from the Web Helpers library replaced an Identicon HTTP handler. I wanted to explicitly purge the handler from search engine results with an HTTP 410 response.