Styling a form into 2 columns

Heya!

I have lots of input fields on my form and am trying to style them into 2 columns so it wouldn’t take as much space on the page. I’ve tried adding HTML code in front of the field (let’s say <div class=”six columns”>) but it automatically adds </div> so none of the fields are actually put in the six-columns div ( even though i’ve added </div> html code after the last field i’d like to have in my first column).
Is there any other way to put fields into two columns or am I just doing something wrong?

Thanks in advance.

http://wordpress.org/extend/plugins/si-contact-form/