在我的gallery div中定义图像样式的正确方法是什么？

I have a div with an id of 'gallery' and I want to style the images inside it. Specifically, I want to give each of the images a 1px solid yellow border except on the bottom because they sit on top of each other, so I don't want to double the border on the bottom.I have a div with an id of 'gallery' and I want