Mark of the Web
From Just Solve the File Format Problem
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 "<!-- saved from url=", and must appear in the first 2048 bytes of the document.
