Your html code should look like:

<!DOCTYPE HTML PUBLIC 
"-//W3C//DTD HTML 4.01 Transitional//EN" 
"http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>
</head>
<body>
</body>
</html>

To insert title, meta and link as children of head using afterEnd you can use:

Sub afterEnd()
   Dim strHTMLLink As String
   Dim strHTMLMeta As String
   Dim strHTMLTitle As String
   Dim objHead As IHTMLElement
   Dim objTitle As IHTMLElement
   Dim objMeta As IHTMLElement
   
   Set objHead = ActiveDocument.all.tags("head").Item(0)
   
   strHTMLLink = _
   vbCrLf & _
   vbTab & _
   "<link>"
   
   strHTMLMeta = _
   vbCrLf & _
   vbTab & _
   "<meta>"
   
   strHTMLTitle = _
   vbCrLf & _
   vbTab & _
   "<title>" & _
   vbCrLf & _
   vbTab & _
   "</title>"
   
   objHead.insertAdjacentHTML "beforeEnd", strHTMLTitle
   Set objTitle = ActiveDocument.all.tags("Title").Item(0)
   objTitle.insertAdjacentHTML "afterEnd", strHTMLMeta
   Set objMeta = ActiveDocument.all.tags("meta").Item(0)
   objMeta.insertAdjacentHTML "afterEnd", strHTMLLink
End Sub

After

   objHead.insertAdjacentHTML "beforeEnd", strHTMLTitle

The HTML will be:

<!DOCTYPE HTML PUBLIC 
"-//W3C//DTD HTML 4.01 Transitional//EN" 
"http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>
	<title>
	</title>
</head>
<body>
</body>
</html>

After

   objTitle.insertAdjacentHTML "afterEnd", strHTMLMeta

The HTML will be:

<!DOCTYPE HTML PUBLIC 
"-//W3C//DTD HTML 4.01 Transitional//EN" 
"http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>
	<title>
	</title>
	<meta>
</head>
<body>
</body>
</html>

After

   objMeta.insertAdjacentHTML "afterEnd", strHTMLLink

Your HTML code will be:

<!DOCTYPE HTML PUBLIC 
"-//W3C//DTD HTML 4.01 Transitional//EN" 
"http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>
	<title>
	</title>
	<meta>
	<link>
</head>
<body>
</body>
</html>

Other methods to accomplish the same thing:

innerHTML, all 3 children at once

innerHTML, Child1, Child 2, Child3

innerHTML, Child3, Child2, Child1

innerHTML, Child1, Child3, Child2 using innerHTML

innerHTML, Child1, Child2, Child3 using outerHTML

insertAdjacentHTML "beforeBegin, strHTML

insertAdjacentHTML "afterBegin, strHTML

insertAdjacentHTML "beforeEnd, strHTML

Valid XHTML 1.0 Transitional        Valid CSS!