Changing image border color

Hi all,

I’ve added a few linked images to the sidebar of my page, and I was wondering how I can get a thin black border around them for contrast. I’ve set border=1, but nothing shows up. I’m guessing that the border is either transparent or white (=background color). How do I make this work? Do I need to edit the style sheet? If so, how/where? Or can I make the change within the links? You can see what I’m talking about here:

https://www.recycledcognition.com/

Thanks for your help,

–recog