[css-transforms] Fix ref to the visual formatting model

Author: xfq

css-transforms/Overview.bs

@@ -89,14 +89,14 @@ Introduction {#intro}
 
 <em>This section is not normative.</em>
 
-The CSS <a href="https://www.w3.org/TR/REC-CSS2/visuren.html">visual formatting model</a> describes a coordinate system within each element is positioned. Positions and sizes in this coordinate space can be thought of as being expressed in pixels, starting in the origin of point with positive values proceeding to the right and down.
+The CSS <a href="https://www.w3.org/TR/CSS2/visuren.html">visual formatting model</a> describes a coordinate system within each element is positioned. Positions and sizes in this coordinate space can be thought of as being expressed in pixels, starting in the origin of point with positive values proceeding to the right and down.
 
 This coordinate space can be modified with the 'transform' property. Using transform, elements can be translated, rotated and scaled.
 
 Module Interactions {#module-interactions}
 ==========================================
 
-This module defines a set of CSS properties that affect the visual rendering of elements to which those properties are applied; these effects are applied after elements have been sized and positioned according to the <a href="https://www.w3.org/TR/CSS2/visuren.html">Visual formatting model</a> from [[!CSS21]]. Some values of these properties result in the creation of a <a href="https://www.w3.org/TR/CSS2/visuren.html#containing-block">containing block</a>, and/or the creation of a <a spec="css21">stacking context</a>.
+This module defines a set of CSS properties that affect the visual rendering of elements to which those properties are applied; these effects are applied after elements have been sized and positioned according to the <a href="https://www.w3.org/TR/CSS2/visuren.html">visual formatting model</a> from [[!CSS21]]. Some values of these properties result in the creation of a <a href="https://www.w3.org/TR/CSS2/visuren.html#containing-block">containing block</a>, and/or the creation of a <a spec="css21">stacking context</a>.
 
 Transforms affect the rendering of backgrounds on elements with a value of ''fixed'' for the 'background-attachment' property, which is specified in [[!CSS3BG]].