Not many of you may of heard of the Mark of the Web feature of Internet Explorer. MOTW is a feature in IE that enhances security. MOTW enables Internet Explorer to force webpages to run in the security zone of the location the page was saved from—as long as that security zone is more restrictive than the Local Machine zone—instead of the Local Machine zone.

When you are developing webpages, the MOTW enables you to test your HTML documents in the security zone where you intend the pages to run. Adding the MOTW to your webpages also enables you to fully test their compatibility with users' security settings.

This is not something new, but has been present in earlier versions of Internet Explorer too.

For a detailed read visit MSDN.