Added a todo in the element() section about writing up the dependency graph and how to deal with cycles.

Author: tabatkins

css3-images/Overview.html

@@ -507,6 +507,11 @@ <h3 id=element-reference><span class=secno>4.3. </span>Using Elements as
      is a syntax error.</p>
 
     <div class=example> TODO: copy an example from the MozHacks article</div>
+
+    <div class=issue> This can pretty obviously result in dependency cycles.
+     An element can try to use itself as a background, for example. I need to
+     add a section about determining the dependency graph and what to do when
+     a cycle is detected.</div>
    </div>
 
    <div>

css3-images/Overview.src.html

@@ -236,6 +236,9 @@ <h3 id=element-reference>Using Elements as Images: The ''element()'' notation</h
 		<div class=example>
 			TODO: copy an example from the MozHacks article
 		</div>
+		<div class=issue>
+			This can pretty obviously result in dependency cycles.  An element can try to use itself as a background, for example.  I need to add a section about determining the dependency graph and what to do when a cycle is detected.
+		</div>
 	</div>
 
 	<div>