How can I make my thumbnails render well?

I'm genereating image thumbnails in a list but they do not come out perfect.

As can be seen from the screenshot, thumbnails may exceed the designated area. I tried setting a somewhat smaller size for the thumbnail but it's still not placing itself well. What can I do? The code that renders the thumbnails looks like:

<img src="http://ift.tt/1IXWrS1" title="Royal Info Service Offered" alt="Royal Info Service Offered">

The parameter s80 is the image size and I probably can't make it smaller. Should I change the CSS? If so, how?