Add note about grid styles applicability.

docs/styles/grid/column_span.md

@@ -2,6 +2,10 @@
 
 The `column-span` style specifies how many rows a widget will span in a grid layout.
 
+!!! note
+
+    This style only affects widgets that are direct children of a widget with `layout: grid`.
+
 ## Syntax
 
 ```sass

docs/styles/grid/grid_columns.md

@@ -2,6 +2,10 @@
 
 The `grid-columns` style allows to define the width of the columns of the grid.
 
+!!! note
+
+    This style only affects widgets with `layout: grid`.
+
 ## Syntax
 
 ```sass

docs/styles/grid/grid_gutter.md

@@ -6,6 +6,10 @@ That is, it sets the space between adjacent cells in the grid.
 Gutter is only applied _between_ the edges of cells.
 No spacing is added between the edges of cells and the edges of the container.
 
+!!! note
+
+    This style only affects widgets with `layout: grid`.
+
 ## Syntax
 
 ```sass

docs/styles/grid/grid_rows.md

@@ -2,6 +2,10 @@
 
 The `grid-rows` style allows to define the height of the rows of the grid.
 
+!!! note
+
+    This style only affects widgets with `layout: grid`.
+
 ## Syntax
 
 ```sass

docs/styles/grid/grid_size.md

@@ -4,6 +4,10 @@ The `grid-size` style sets the number of columns and rows in a grid layout.
 
 The number of rows can be left unspecified and it will be computed automatically.
 
+!!! note
+
+    This style only affects widgets with `layout: grid`.
+
 ## Syntax
 
 ```sass

docs/styles/grid/row_span.md

@@ -2,6 +2,10 @@
 
 The `row-span` style specifies how many rows a widget will span in a grid layout.
 
+!!! note
+
+    This style only affects widgets that are direct children of a widget with `layout: grid`.
+
 ## Syntax
 
 ```sass