[css-tables] Added note on blockification -- fixes #222

Author: FremyCompany

css-tables-3/Overview.bs

@@ -336,6 +336,11 @@ spec:css21; type:property; text:max-width
 				</li>
 			</ol>
 
+			<div class="advisement">
+				Please note that some layout modes such as flexbox and grid <a href="http://www.w3.org/TR/css-display-3/#blockify">override the display type</a> of their children.
+				These transformations happen before the table fixup.
+			</div>
+
 		<!--------------------------------------------------------------------------------->
 		<h4 id="fixup-examples">Examples</h4>