In all the most commonly used browsers, it is possible to increase or decrease the font size by holding down Ctrl (Cmd in the OS X operating system) and pressing either + or -. Another convenient option is to use the mouse: hold down the Ctrl key and move the scroll wheel at the same time. You can return to normal size by pressing Ctrl and 0 at the same time.
The European Commission's Taxation and Customs Union provides a number of interesting e-learning courses on tax and customs topics on the e-learning section of their website.