squeezr is most effective on sites with big images and heavy use of CSS3 media queries, which is typical for responsive or mobile web designs. However, in most cases at least some small savings can be achieved through image recompression and CSS minification. If the savings calculated by the test pilot aren't that huge, it's either because there's not much to save about your site (e.g. images are too small for downscaling and you don't use media queries), or because you just did a pretty good job already! ;)