Hi
Sorry my bad (I think). I've been looking for the page where I've seen 2 H1 tags, but cannot find it right now. So it was fixed or I looked it wrong in my first check.
Anyway, back to the question. What are You using to build Your canonical tag ? We or joomla are not providing such functionality by default and on Your site I can see it's working wrong obviously, becuase this function is to tell SEO robots which page is a primary for viewed one. Example:
for page
http://www.testsite.com/article-xxx?print=1 the canonical will be:
http://www.testsite.com/article-xxxOn Your site I can see canonical tags only when I look into category view where there is no side options for such page and this tag is not required, but an article view doesn't have canonical tags at all and this is the place what it's most needed. Anyway robots are smart enough to recognize joomla side article links, so canonical tags are not really a "must have" option when You are not using any none standard extensions.