Transparent png submit button sprite image

I'm trying to use a transparent png sprite image as the background to my submit button for the normal, hover, and active states. I've been able to customize the submit button through the css just fine, but there seems to be some default box/button still behind my custom submit button image.

Take a look here,
http://www.zilchgravity.com/Test/LKJ-WP/contact/

Is there a way to use your own sprite image as a background for the submit button without this happening? I've been trying to figure it out for a few hours now. Im pretty new to gravity forms, But I can see myself and others trying to use his technique quite often

Thanks in advance

Rob, you're kidding me. wow, I feel like a complete idiot.
For some reason I kept thinking that there was a default submit button back there, like the kind put out by the operating system.. apart from that border, I swear I saw a different colored button, but it was just the negative space inside the border playing ticks on my eyes. border: 0; did the trick. Thanks!