homan98

To style a specific image, you would need to style it specifically. Add an class or style it.

#content .gallery .gallery-icon img,img.attachment-thumbnail{}

you might have to use ftp to edit the file.

#content .gallery .gallery-icon img,img.wp-post-image,img.attachment-thumbnail{border:1px solid #ccc;padding:6px}

remove border:
#content .gallery .gallery-icon img,img.wp-post-image,img.attachment-thumbnail{}

line: 189 from your stylesheet

On Chrome Browser, you can always right click on the element and use inspect element to check.