The Grunion Contact Form plugin adds this stylesheet inline with the form.
<style>
input[type='text'] { width: 300px; }
input { margin-bottom: 0 !important; font-size: 12px !important; font-family: 'Lucida Grande',Verdana,Arial,'Bitstream Vera Sans',sans-serif; }
textarea { height: 200px; width: 400px; }
input[type='radio'] { float: left; }
label { margin-bottom: 3px; }
input{type='checkbox'] { display: inline-block; }
</style>
Ignoring the issue of adding inline stylesheets (we all do it, really), the rules are too broad. Any other form elements on the page not affected by their own styling will be impacted by these rules as well.
Since the form does have a "contact-form" class on it, that class should be used in these rules to make them more specific to the contact form in general.
As in:
<style>
.contact-form input[type='text'] { width: 300px; }
.contact-form input { margin-bottom: 0 !important; font-size: 12px !important; font-family: 'Lucida Grande',Verdana,Arial,'Bitstream Vera Sans',sans-serif; }
.contact-form textarea { height: 200px; width: 400px; }
.contact-form input[type='radio'] { float: left; }
.contact-form label { margin-bottom: 3px; }
.contact-form input{type='checkbox'] { display: inline-block; }
</style>