problems with plasma theme in explorer and Safari

Hi

I have just installed plasma in Firefow it looks fantastic, but I am having some issues in chrome and safari. The structure of the theme is in these 2 web browsers non consistent and the main content is occupying the main menu space, which makes everything a bit messed up.

At the beguining I tought it was my installation www.territoriosyfronteras.com, but then I checked the plasma site and same thing happened there. (see attachements) or visit http://demo.drupalyag.com/plasma/ in safari and/or chrome

I love the theme and would really like to find a solution for it.
Anybody can help me?

Thanks in advance