You want responsive design. Essentially, responsive design is an approach of making the web-page look good in any browser or device. If you want to make the images shrink proportionally, then you need to set their width and height to certain percentage of their container, which, on the other hand should be a percentage of its container and so on. It is slightly more difficult to make the text shrink or enlarge upon window size change, since it you need media queries for that.
Read this tutorial to learn about responsive design and click on next chapter a few times, to make sure you read enough material about the topic in general. Use media queries to set the font-size property depending on specific cases you define according to your taste and needs.