[css-backgrounds-3][editorial] small wording tweaks

Author: fantasai

css-backgrounds-3/Overview.bs

@@ -776,8 +776,8 @@ Positioning Area: the 'background-origin' property</h3>
 	</pre>
 
 
-	Determines the <dfn>background positioning area</dfn>,
-	which determines the area within which any background images are positioned.
+	This property determines the <dfn>background positioning area</dfn>:
+	the area within which any background images are positioned.
 	For elements rendered as multiple [=box fragments=]
 	(e.g., inline boxes on several lines, boxes on several pages),
 	specifies which boxes 'box-decoration-break' [[CSS-BREAK-3]] operates on
@@ -1700,8 +1700,8 @@ Corner Shaping</h3>
 	the outer border radius minus the corresponding border thickness.
 	In the case where this results in a negative value,
 	the inner radius is zero.
-	(In such cases the inner curve's center might not coincide
-	with that of the outer curve.)
+	(In such cases the center of the border’s inner curve might not coincide
+	with that of its outer curve.)
 	Likewise the [=content edge=] radius is
 	the [=padding edge=] radius minus the corresponding [=padding=],
 	or if that is negative, zero.
@@ -2714,7 +2714,7 @@ Blurring Shadow Edges</h4>
 	the image that would be generated by applying to the shadow
 	a Gaussian blur with a standard deviation equal to half the blur radius.
 
-	Note:his means for a long, straight shadow edge,
+	Note: This means for a long, straight shadow edge,
 	the blur radius will create a visibly apparent color transition
 	approximately the twice length of the blur radius
 	that is perpendicular to and centered on the shadow's edge,