I modified a Wordpress theme, and it works correctly on my server in Chrome, IE9/10 and Firefox (http://office-porn.net)

I am using the same child theme on a different server, and responsiveness does not work correctly in IE9/10 and Firefox (the website does not look right when I make the screen narrower). This site is at http://marie-luv.com

Does anybody have an idea how to get around this one?

Thank you.