update: tile-layout-using-inline-block with a side note

snippets/tile-layout-using-inline-block.md

@@ -10,6 +10,8 @@ Align items horizontally using `display: inline-block` to create a 3-tile layout
 - Use `width: calc((900px / 3))` to divide the width of the container evenly into 3 columns.
 - Set `font-size: 0;` on `.tiles` to avoid whitespace.
 - Set `font-size: 20px` to `h2` in order to display the text.
+- Note: If you use relative unit like `em` then using `font-size: 0;` to fight whitespace between the blocks might cause a side effect 
+
 
 ```html
 <div class="tiles">