In the year 2009 we celebrate the 400^th anniversary of the Galileo’s important observations in astronomy, thus it is declared as the year of astronomy, under the guidance of UNESCO. Galileo made his own refracting telescope and improved it several times during the year 1609, so that he was able to see more details on the Moon as anyone before him. He found that the Moon wasn’t an ideal sphere as it was believed for all celestial bodies, but it had the mountains, valleys and craters instead. In the following years he made several other discoveries in astronomy, for instance the moons of Jupiter, the phases of Venus, etc., all of which aided for the heliocentric model of Universe. We have made web textbook in Slovene to encourage young people, particularly primary school pupils, to learn about the Galileo’s important contributions to the development of modern science. The web textbook is a popular didactic tool because of incorporation of multimedia elements, simulations, etc., and not only text. Our web textbook consists of three topics: Galileo’s life, his scientific work, and the opinion of other scientists about him.