Website Looks Different in Mozilla Firefox & Internet Explorer?

Hi,

I am using Buddypress Magazine theme, and have set it up how I want it to look in Mozilla Firefox, however when I look at the website in Internet Explorer it looks a mess.

The body text on the homepage is the same colour as the header text, there is a big gap between the header text and the body text, the text in the sidebar is much bigger than it should be, and the footer is the wrong size.

My site is at 4.biz. I have attached some screenshots below to demonstrate what I mean.

Mozilla:

Internet Explorer:

Mozilla:

Internet Explorer: