Updated versioning finding

I've added the section I mentioned on partial understanding.  I also
tied this in with the internet robustness principle and provided a
couple of good practice notes around "liberal" in accepting and
"conservative" in producing.

 

It's pretty rough around the edges, but I think it really completes the
story about compatibility.

 

http://www.w3.org/2001/tag/doc/versioning

 

Cheers,

Dave