Content pushed to the left side ONLY on IE. Please help!

Dear all,
since this is my first time here, Hi to everyone!

I have been modifying a template called “Northern-Web-Coders” all through this afternoon.
I got to the stage where I feel happy with what I have. And it is looking great (by my standards, anyway) on a number of browsers. Safari (Mac), Firefox (Mac), Netscape (Mac).
But the main content posts and sidebar seem to be a bit pushed to the left in IE (Mac 5.2.3).

Would someone be kind enough to check this and tell me what they think might be causing this hassle?
Thank you.

I will look forward for your help and I will, of course, post any solutions you may find and share the problem solving steps.

The URL where the site is hosted for now is
http://www.o-meu-casamento.com/wordpress

Thank you once again in advance.

Yours truly,

André Toscano