Change size of contact form boxes

This page: http://www.kau-hawaii.com/wordpress/contact/

I don’t want the contact form to fill the entire page. What code do I use to say make it 50%

I tried this but it didn’t work:
#top .avia_ajax_form .text_input}
margin-bottom: 0;
display: inline;
min-width: 50px;
padding: 13px;
border-radius: 2px;
}