GRASS HTML Tutorial, based on freely available (and distributable) data. The structure of this tutorial is functional both for a new GRASS user and for a GRASS expert. The purpose of this work is to simplify the first approaches to GRASS, trough a series of examples and practical environmental applications of this GIS. Data is the free data set Spearfish60 downloadable from official GRASS website. A troubleshooting FAQ page is also available.