[css-values] Reduce expository prose in fragment-handling section. Indent under Relative URLs since they are relative URLs (that have special handling).

Author: fantasai

css-values/Overview.bs

@@ -588,13 +588,10 @@ Relative URLs</h4>
 		The same image will be used regardless of the URL of the source document containing the <code>&lt;body></code>.
 	</div>
 
-<h4 id='local-urls'>
-Fragment URLs</h4>
+<h5 id='local-urls'>
+Fragment URLs</h5>
 
-	In some CSS-using languages like SVG,
-	one often needs to refer to elements in the host document directly
-	(such as to reference a <{linearGradient}> element).
-	To facilitate this and work around some common eccentriticites in browser URL handling,
+	To work around some common eccentriticites in browser URL handling,
 	CSS has special behavior for fragment-only urls.
 
 	If a ''url()''’s value starts with a U+0023 NUMBER SIGN (<code>#</code>) character,
@@ -611,7 +608,7 @@ Fragment URLs</h4>
 	it must serialize as just the fragment.
 
 	<details class=note>
-		<summary>What "browser eccentricities"?</summary>
+		<summary>What “browser eccentricities”?</summary>
 
 		Theoretically, browsers should re-resolve any relative URLs,
 		including fragment-only URLs,
@@ -624,12 +621,10 @@ Fragment URLs</h4>
 		(pointing at the previous base URL)
 		and break in many of the places they're used.
 
-		Refusing to re-resolve relative URLs makes sense in many cases
-		(it will usually give the <em>desired</em> behavior
-		when the URL is path-relative),
-		but fragment-only URLs express a clear semantic
+		Since fragment-only URLs express a clear semantic
 		of wanting to refer to the current document
-		regardless of what its URL is.
+		regardless of what its current URL is,
+		this hack preserves the expected behavior at least in these cases.
 	</details>
 
 <h4 id="url-empty">