Add the normative link to "top layer" (#26251)

* Add link to "top layer"

* Update spec link

files/en-us/web/css/css_containment/index.md

@@ -145,18 +145,18 @@ Its possible values are:
 
 ### Relevant to the user
 
-The specification refers to the concept of [relevant to the user](https://www.w3.org/TR/css-contain-2/#relevant-to-the-user). An element that is relevant to the user should be rendered, as it visible, and/or being interacted with by the user.
+The specification refers to the concept of [relevant to the user](https://w3c.github.io/csswg-drafts/css-contain/#relevant-to-the-user). An element that is relevant to the user should be rendered, as it is visible, and/or being interacted with by the user.
 
 To be precise, an element is relevant to the user if any of the following are true:
 
 - The element appears in the viewport, or a user-agent-defined margin around the viewport (50% of the viewport dimensions, to give the app time to prepare for when the element visibility changes).
 - The element or its contents receive focus.
 - The element or its contents are selected, for example by dragging over the text with the mouse cursor or by some other highlight operation.
-- The element or its contents are placed in the top layer.
+- The element or its contents are placed in the [top layer](https://w3c.github.io/csswg-drafts/css-position-4/#top-layer).
 
 ### Skips its contents
 
-The specification refers to the concept of [skips its contents](https://www.w3.org/TR/css-contain-2/#skips-its-contents). This means that the element referred to is not relevant to the user and will not be rendered to improve performance.
+The specification refers to the concept of [skips its contents](https://w3c.github.io/csswg-drafts/css-contain/#skips-its-contents). This means that the element referred to is not relevant to the user and will not be rendered to improve performance.
 
 To be precise, when an element skips its contents: