Acid1

250px|thumb|right|Example of a failed Acid1 test 250px|thumb|right|Easter egg (media)|Easter egg in Internet Explorer 5 for Mac Acid1, originally called the Box Acid Test, is a test page for web browsers. It was developed in October 1998 and was important in establishing baseline interoperability between early web browsers, especially for the Cascading Style Sheets 1.0 specification. As with acid tests for gold which produce a quick and obvious assessment of the quality of a piece of metal, the web acid tests were designed to produce a clear indication of a browser's compliance to web standards.

==History== Acid1 tests many features on one page against a reference image. Acid1 was developed by Todd Fahrner, who was frustrated with the lack of stringent tests to improve browser interoperability. After looking at tests developed by Braden McDaniel that used reference renderings to clarify the intended result, Fahrner developed a comprehensive test that resulted in a quirky-looking graphic. In 1999, the test was incorporated into the CSS1 test suite. The text used in Acid1 is an allusion to T. S. Eliot's poem The Hollow Men. Acid1 is included as an offline Easter egg in Internet Explorer 5 for Mac OS, accessible by typing 'about:tasman', with the text replaced by the names of the developers.