[css-display-3] Revert inadvertent change to dfn IDs. See #3883 and speced/bikeshed#1466

Author: fantasai

css-display-3/Overview.bs

@@ -49,15 +49,19 @@ Introduction</h2>
 
 	<p><em>This section is normative.</em>
 
-	CSS takes a source document, organized as a <dfn export for=CSS lt="element tree">tree</dfn> of <dfn export for=CSS lt="element">elements</dfn> and <dfn export for=CSS lt="text node">text nodes</dfn>,
-	and renders it onto a <a href="https://www.w3.org/TR/CSS2/intro.html#canvas">canvas</a> (such as your screen, a piece of paper, or an audio stream).
+	CSS takes a source document, organized as
+	a <dfn id="element-tree" oldids="css-element-tree" export for=CSS lt="element tree">tree</dfn>
+	of <dfn id="elements" oldids="css-element" export for=CSS lt="element">elements</dfn>
+	and <dfn id="text-nodes" oldids="css-text-node" export for=CSS lt="text node">text nodes</dfn>,
+	and renders it onto a <a href="https://www.w3.org/TR/CSS2/intro.html#canvas">canvas</a>
+	(such as your screen, a piece of paper, or an audio stream).
 	To do this, it generates an intermediary structure,
-	the <dfn export for=CSS>box tree</dfn>,
+	the <dfn id="box tree" oldids="css-box-tree" export for=CSS>box tree</dfn>,
 	which represents the formatting structure of the rendered document.
-	Each <dfn export for=CSS>box</dfn> in the <a>box tree</a>
+	Each <dfn id="box" oldids="css-box" export for=CSS>box</dfn> in the <a>box tree</a>
 	represents its corresponding [=CSS/element=] (or <a>pseudo-element</a>)
 	in space and/or time on the canvas,
-	while each <dfn export for=CSS>text run</dfn> in the <a>box tree</a>
+	while each <dfn id="text-run" oldids="css-text-run" export for=CSS>text run</dfn> in the <a>box tree</a>
 	likewise represents the contents of its corresponding <a>text nodes</a>.
 
 	To create the <a>box tree</a>,
@@ -107,7 +111,7 @@ Introduction</h2>
 	which is assigned the same styles as the generating <a>text nodes</a>.
 	If the sequence contains no text, however, it does not generate a <a>text run</a>.
 
-	An <dfn for=CSS lt="anonymous|anonymous box" export>anonymous box</dfn> is a box that is not associated with any element.
+	An <dfn id="anonymous" oldids="css-anonymous" for=CSS lt="anonymous|anonymous box" export>anonymous box</dfn> is a box that is not associated with any element.
 	<a>Anonymous boxes</a> are generated in certain circumstances
 	to fix up the <a>box tree</a> when it requires a particular nested structure
 	that is not provided by the boxes generated from the <a>element tree</a>.
@@ -1168,7 +1172,7 @@ Appendix A: Glossary</h2>
 		<dt><dfn lt="absolutely positioned | absolutely positioned element | absolutely positioned box">absolutely posititioned</dfn>
 		<dd>
 			A box is <a>absolutely positioned</a>
-			if its 'position' property is either ''absolute'' or ''fixed''.
+			if its 'position' property is either ''position/absolute'' or ''position/fixed''.
 			Absolutely positioned boxes are also <a>out-of-flow</a>.
 
 		<dt><dfn>document order</dfn>