Back to the original question though. Windows specifically allows you to "Send To" > Email on any file on your computer this requires a default program to be selected for email. This won't work if you only access email through a browser vs a thick client such as Outlook, Mail or Thunderbird. If you want to send a webpage directly as an email attachment from the browser I don't believe that is supported out of the box (and that would be browser dependent). For example, in Chrome there are a number of extensions you can add to add that functionality.