Icon scaling via CSS for Mobile and iPad

Hello, so i am customizing the CatchBase theme, and I need to figure out how to get the images on my pages to scaled to smaller size when on Mobile and iPad browsers. Any suggestions on CSS code and what to do would be greatly appreciated. Well, it won't show my image links. I just have a bunch of 300px images in a grid, some act as a button that link to another page too. When i scale the window down to where it would be mobile-size, the images stay at 300px.