Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Valid, Accessible and Compatible, or VAC, is an online project aimed at encouraging the development of standards compliant websites as well as accessible ones. Gaining popularity in the summer of 2006, VAC has served as the universal tag to identify websites whose owners have taken the time and effort to create websites that can be viewed properly, navigated easily, and accessed via any browser.