standards tested Acid2 tests a variety of web standards published by the World Wide Web Consortium and the Internet Engineering Task Force. With the exception of CSS 2.1, all web standards tested were codified before the year 2000. CSS 2.1 was a candidate recommendation at the time of Acid2's release, and was still a candidate recommendation as of 23 April 2009. Specifically, Acid2 tests these functions on your browser; Alpha transparency in PNG-format images, which is seen when the eyes of the smiley face use alpha transparency, which is part of the 1996 Portable Network Graphics specification. Alpha transparency blends the eyebrows into the face smoothly and elegantly. This was a significant issue because Internet Explorer 6, the most widely used web browser at the time Acid2 was released, did not support alpha transparency. This deficiency was rectified in Internet Explorer 7, bringing Internet Explorer in line with other web browsers in this regard. object element which, once again, the eyes also test support of the HTML object element. The object element has been a part of HTML since HTML 4 was released in 1998, yet by 2005 it still was not completely supported in all web browsers. The creators of Acid2 considered object element support important because it allows for content fallback—if an object fails to load, then the browser can display alternative (generally simpler, more reliable) content in its place. Data URIs, where the actual images that form the eyes are encoded as data URIs, which allow multimedia to be embedded in web pages rather than stored as a separate file. Acid2 tests the most common case, where a binary image is base64-encoded into text and then that encoded text is included in a data URI in the web page. Although the IETF published the data URI specification in 1998, they never formally adopted it as a standard. Nonetheless, the HTML 4.01 specification references the data URI scheme, and data URI support has now been implemented in most browsers.'Absolute, relative, and fixed CSS positioning, which mean the web developer specifies the exact X and Y coordinates where an element is to be placed into the page, the web developer specifies an X and Y offset from the usual position of the element, and the element is placed relative to the browser window, and scrolls with the window rather than with the rest of the page. The CSS box