Help on IE 7

I am coding a website for the first time in HTML5 and CSS3. It looks OK on IE8, Safari and Firefox but on EI7 and below the fonts appear so big. I mean bigger than 10em in size.

Some one please help.

10em? Are these headings? Do you have a link to the site?

Here is the link. Just view it on IE 6 and you’ll see.

I get a mcafee warning message on that link.