Contact form 7 image for submit button

Hello guys I really need your help today.

I want to change the regular submit button for an image in the Contact Form 7.

I followed some of the advices founded here in this forum, so I added this to the cf7 style.css

.contactSubmit{
padding:0px 0 0px 0px;
color:#FF0000;
border:none;
width:231px;
height:35px;
image-align:center;
background-image:url(https://prolocalweb.com/roofing/wp-content/uploads/2012/09/contact_submit1.gif);
background-repeat:no-repeat;
}

And this to the form: <p>[submit class:contactSubmit “”]</p>

SEE what I got here: https://prolocalweb.com/roofing/

What do I am doing wrong? What do I need to do?

THANKS in advance for whom may take care on my need!