Javascript is a programming language that can be used to add interactivity. Fortunately, the web offers many javascripts, so you won't have to become a programmer to use them. Javascript is NOT Java. Java is a cross-platform programming language developed and marketed by Sun Microsystems. Javascript can interact with a Java applet.
Several resources related to javascript are available online.
Three javascripts featured on this tutorial page were obtained from this site. Choose two of the five javascripts from this page or make your own choice from The JavaScript Source. Follow the instructions in the code given on the associated web page.