fix(css): for sticky value an inset property need to be set

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

@@ -56,6 +56,8 @@ position: unset;
 
     This value always creates a new [stacking context](/en-US/docs/Web/CSS/CSS_positioned_layout/Understanding_z-index/Stacking_context). Note that a sticky element "sticks" to its nearest ancestor that has a "scrolling mechanism" (created when `overflow` is `hidden`, `scroll`, `auto`, or `overlay`), even if that ancestor isn't the nearest actually scrolling ancestor.
 
+    At least one [inset](/en-US/docs/Web/CSS/inset) property on the axis in which the element needs to be kept in view needs to have non `auto` value. Otherwise, if both inset properties are `auto` on an axis then the `sticky` value behaves as `relative` on that axis.
+
 ## Description
 
 ### Types of positioning