[css-images-3][editorial] Address smfr's editorial comments from a426128#diff-8ca754d7bf316f5f3b1cc2c313a70deaa0d9377888c440a0449bdf22111b3776

Author: tabatkins

css-images-3/Overview.bs

@@ -220,17 +220,17 @@ Images can contain metadata
 such as resolution and orientation
 which specifies how to render the image.
 Some image formats are flexible in where this metadata can be placed in the file;
-however, if the metadata occurs <em>after</em> the bulk of the actual image data,
+however, if the metadata occurs <em>after</em> the actual image data,
 it harms the UA's ability to “progressively decode” the image
 and display it as the image's data streams in.
 
 To reduce the impact of this issue:
 
 * Authors <em>must</em> produce their image files
-	so that such metadata occurs first in the image file.
+	so that such metadata occurs before the image data in the image file.
 	(Note: This is the default for most images already.)
 * User agents <em>should</em> ignore any layout-impacting metadata (such as orientation or resolution)
-	that occurs after the actual image data begins in the file.
+	that occurs after the image data begins in the file.
 	(Note: This rule does not impact metadata that does not affect layout,
 	such as color space information.)