[css-images-4] Fix errors.

Author: tabatkins

css-images-4/Overview.bs

@@ -12,8 +12,8 @@ Editor: fantasai, Mozilla, http://fantasai.inkedblade.net/contact
 Abstract: This is a delta spec over Images 3; when next published, it will be a real spec with everything filled in, but for now removing duplication is more important than having a complete spec.
 !Issue Tracking: <a href="http://www.w3.org/Style/CSS/Tracker/products/27">http://www.w3.org/Style/CSS/Tracker/products/27</a>
 Previous Version: http://www.w3.org/TR/2012/WD-css4-images-20120911/
-Ignored Terms: <offset>, background positioning area, border image area, <meetorslice>, <ending-shape>, Map, <image>, invalid image, invalid images, concrete object size, linear-gradient(), radial-gradient(), intrinsic dimensions, default object size
-Link Defaults: css21 (property) display
+Ignored Terms: <offset>, background positioning area, border image area, <meetorslice>, <ending-shape>, Map, <image>, invalid image, invalid images, concrete object size, linear-gradient(), radial-gradient(), intrinsic dimensions, default object size, CSS
+Link Defaults: css21 (property) display, css21 (dfn) stacking context
 </pre>