[css-images-4][editorial] Shuffle dfns

Author: fantasai

css-images-4/Overview.bs

@@ -174,7 +174,7 @@ Resolution/Type Negotiation: the ''image-set()'' notation {#image-set-notation}
 	for example, if the user is on a slow mobile connection,
 	they may prefer to receive lower-res images
 	rather than waiting for a large proper-res image to load.
-	The ''image-set()'' function allows an author to ignore most of these issues,
+	The <dfn>image-set()</dfn> function allows an author to ignore most of these issues,
 	simply providing multiple resolutions of an image
 	and letting the UA decide which is most appropriate in a given situation.
 
@@ -188,7 +188,7 @@ Resolution/Type Negotiation: the ''image-set()'' notation {#image-set-notation}
 	The syntax for ''image-set()'' is:
 
 	<pre class='prod'>
-	<dfn caniuse="css-image-set">image-set()</dfn> = image-set( <<image-set-option>># )
+	<<image-set()>> = image-set( <<image-set-option>># )
 	<dfn>&lt;image-set-option></dfn> = [ <<image>> | <<string>> ]
 	                     [ <<resolution>> || type(<<string>>) ]
 	</pre>