Added Florian's 'collision' property idea.

Author: bert-github

css3-layout/Overview.src.html

@@ -2083,6 +2083,21 @@ <h3 class=grid>Stacking elements on top of a grid: 'grid-area'</h3>
 value definition">per grammar</abbr>
 </table>
 
+<div class=issue>
+<p>At the Aug 2012 ftf, Florian suggested a property 'collision: auto
+| collide | avoid' to switch between overlapping and not overlapping.
+(It would avoid collisions for absolutely positioned elements as
+well.) Instead of two properties 'flow' and 'grid-area', we could have
+just one, and then toggle between overlapping and flowing with the
+'collision' property.
+
+<p>It may be attractive, because the same 'collision' property could
+also improve absolute positioning and add functionality to floats, but
+on the other hand it is a property that works indirectly, by modifying
+the meaning of another property, and as such the pair 'flow' and
+'grid-area' may be easier to learn.
+</div>
+
 <p>The 'grid-area' property can take an element out of the flow and
 position it relative to a grid. The 'z-index' is used to determine the
 stacking level. If the element has no <span>grid ancestor,</span> the