Several problems (pointed out by Dave Beckett first):

Different tabs don't do anything (they always show the english). Perhaps we 
should make this a toggle only for the consice format? Then the rest can 
load the owl.owl and rdf.rdf etc.

That will solve the problem that the address bar and the side bar aren't in 
synch!

We'll have to come up with a special ontology for datatypes, perhaps, to 
solve the second problem for them. Or have a popup window there.