There were a number of e-mails on this thread regarding how Collections and other interfaces worked with respect to properties being exposed. I have now updated the HTML5 spec to take into account the new features in WebIDL that expose these properties. Please let me know if I missed one.
Cheers, -- Ian Hickson U+1047E )\._.,--....,'``. fL http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'