Any question answered...

Yes.

Bookmark this:

[code]javascript:(function(){location.href=location.href.replace('www', 'preview')})();[/code][Edit] Or bookmark this and edit the bookmark and copy in the above. Then you can use a key word or just press the bookmark to change the url.

I'm sure some javascriptmonkey could rewrite it so that it toggles between preview / www, depending on which the url says.

Hmm, thanks, but that's not working for me.