Mark of the Web

The Mark of the Web is a specially-formatted comment that can be added to a copy of an HTML document, to record the location of the original. The idea is that web browsers can use it as a hint that the document should be handled in a more restrictive security mode than its location might otherwise suggest.

Identification
A Mark of the Web comment begins with " ", and must appear in the first 2048 bytes of the document.

Links

 * MSDN: Mark of the Web