title: Why does Microsoft have IHTMLDocument, IHTMLDocument2, ... , IHTMLDocument8?
body: <p>What is the meaning of the number in the end of the interface name? I see that <code>IHTMLDocument3-7</code> have no members (<a href="http://msdn.microsoft.com/en-us/library/aa752514%28v=VS.85%29.aspx" rel="noreferrer">see example for #5</a>), and <code>8</code> has gesture related members. Is the number derived from Windows version?</p>