Padding images in Lite 1.0 CSS – how to?

Using Light 1.0 theme.

I want all images to have a padding of 10 pixels. Reading theough the Codex “Using Images” tutorial, I see that I need to modify the image tag in the theme CSS.

The theme CSS has a class that begins with
“a img {” but not one that starts with just “img {“. I do not understand much about CSS so I don’t appreciate the significance of the leading “a”.

Changing that piece of code has no effect on the images in my posts.

Ideally, this is what I want:

img {
padding: 10px;
border: 0;
}

How can I produce that effect in the Lite 1.0 CSS?

Thanks