Added text to Challenge #6.

conformance-challenges/index.html

@@ -435,7 +435,7 @@ <h3>Silver Research Findings</h3>
 	    <p>Evolving Technology of the rapidly changing web must constantly be evaluated
 	      against the capabilities of assistive technology and evolving assistive
 	      technology must be evaluated against the backward compatibility of existing
-	      web sites.</p>
+	      web sites. This challenge is further complicated by versions of content adapted for multiple device modalities, eg. mobile vis a vis full-screen view. There may also be multiple language versions of each of these content views to be evaluated with browsers and assistive technologies commonly used with specific languages.</p>
 	</section>
 
 	<section class="appendix" id="Appendix-A">