[css-position-3][editorial] fix link

Author: tabatkins

css-position-3/Overview.bs

@@ -356,7 +356,7 @@ Containing Blocks of Positioned Boxes</h3>
 				as a result, [=fixed=] boxes do not move when the document is scrolled.
 
 				Note: In this respect, they are similar to
-				[[css-backgrounds-3#the-background-attachment|fixed background images]]
+				[[css-backgrounds-3#background-attachment|fixed background images]]
 				(''background-attachment: fixed'').
 
 			* in [=paged media=],