Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Acid3 is a test page from the Web Standards Project that checks how well a web browser follows certain selected elements from web standards, especially relating to the Document Object Model and JavaScript. When successful, the Acid3 test displays a gradually increasing percentage counter with colored rectangles in the background. The percentage displayed is based on the number of subtests passed. It does not represent an actual percentage of conformance as the test does not keep track of how many of the subtests were actually started (100 is assumed). In addition to these the browser also has to render the page exactly as the reference page is rendered in the same browser. Like the text of the Acid2 test, the text of the Acid3 reference rendering is not a bitmap, in order to allow for certain differences in font rendering. Acid3 was in development from April 2007, and released on 3 March 2008. The main developer was Ian Hickson, who also wrote the Acid2 test. Acid2 focused primarily on Cascading Style Sheets, but this third Acid test also focuses on technologies used on modern, highly interactive websites characteristic of Web 2.0, such as ECMAScript and DOM Level 2.