HyperText is for exploring, and you are unlikely to get into trouble by clicking on whatever link interests you. And don't worry about damaging any hardware or software on your computer by randomly clicking on links. Exactly where these navigation buttons are located depends on your browser. The following image shows the menu of Netscape Navigator. Your browser is probably similar.
Most browsers are very intuitive, so just click on things to see what they do.
If your browser is set up to distinguish visited from unvisited links, the color of links you have already visited will be different from unvisited ones. The exact colors depend on your browser and the document you are viewing. Two common colors for visited and unvisited links are red and blue, respectively, but the colors depend on the browser and how the document that you are viewing has been written. At the top and bottom of main pages there may be additional navigation buttons. In addition to words, other objects on a page may be clickable links.