JavaScript language may be incorporated into web (html) pages to give them an interactive, dynamic, and utilitarian effect.
These buttons (to the left) are just one example of how JavaScript is being used to add more life to a hyperlink. The effect may not be noticable using some browsers, so if these buttons appear just as all buttons do, and look no different than all the rest, then your browser is either just not into cool buttons or you have your personal settings preventing your viewing these things.
On the other hand, if you are interested in seeing exactly how this is coded, then click the buttons starting with the top one "About these buttons". (Even if your browser does not show the effect, you can still read about the coding.)