It can either be the nightly javadocs or what we produce with the upcoming 'stable build'.
I'm not sure how many folks even use it from the web with IDE's having it built in… probably more helpful for troubleshooting in the forums and reference on the wiki.
Yes I would think a JavaDoc for the website should refer to the stable just like any other static information like the wikipages will. I hope this won't make developers take lightly on javadoc updates for the nightlies though.
Sorry, but I voted wrongly,
I also think that it should display the stable javadoc, who wants to see the nightly (like me }:-@) can still use their IDE + nightly sourcode…
Yeah, I would've said the stable as well…though I voted for nightly, as that's what I personally want to see 
I've been impressed by the amount of documentation commits i've seen lately, so it got me thinking
what is up currently?
What you see now is the Javadoc for 2.0.1, which is the default download on the Google Code page