div borders on gallery thumbs

Hello. This is my first post so bear with me. I started a wp blog two days ago and have been tweaking things. I’ve searched the forums and found several “solutions” of which none worked. I’m trying to remove the borders on the thumbnails in gallery posts. I tried the ‘Gallery Shortcode Style to Head’ but that didn’t seem to work. The only plugin I currently have running is ‘jQuery Lightbox For Native Galleries’ to avoid the attachment pages. any help woud be appreciated. My CSS is very rusty. I’ve been a carpenter longer than I was a designer. here is my site.

here is a page with an example of the thumbs in question

thanks

tim