Applets are programs written in Java that run on your own machine but they need the Java Virtual Machine to run them. This should be standard on most university or college computers. The Java VM can be downloaded free from http.java.sun.com. You only need to download it; it will sort itself out on your machine.
The individual applet programs can be downloaded on to your own machine so that you do not need to operate on-line. This has the advantage that you can make adjustments to the size of the diagram. The applet is run by a small *.html file. You can edit this (using NotePad, in which it comes up automatically if you select View Source from the View menu). You will see WIDTH and HEIGHT parameters in pixels. The applet should be resizable in the range from about 1000 to 400 pixels in WIDTH and you should change the HEIGHT parameter roughly in proportion. In most of the applets there will be control parameters that highlight different features. These generally take the values 0 or 1 and you can play about with them to see what they do. To be able to make these adjustments download the applet (*.jar file) and the controlling file (*.html file).