Here's how to install a nifty little program called Navigation Popups, that lets you peer into Wikipedia articles when you hover the mouse cursor over internal links:
{{subst:navpop}}
to your current skin's .js page. See Wikipedia:Tools/Navigation popups#Installation for full installation instructions.For this to work, make sure you have not disabled javascript in your browser. By the way, Navigation Popups is recursive: it works on links that appear in its popups.