Turned off WYSIWYS and pasted the button - code stayed verbatim - sure enough, the continue shopping button worked like it was supposed to - BUT the whole cart opened and closed in a new window, not a lightbox/thickbox.
somehow, joomla is ignoring the javascript, even tho it remains there in the code.
BTW - site is live, so I had to revert the button it's previous dodgy state (for now)