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. 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.{{cite web • The
object element: 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,{{cite web •
Data URIs: 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.{{cite web •
Absolute, relative, and fixed CSS positioning: Absolute positioning means that the
web developer specifies the exact X and Y coordinates where an element is to be placed into the page. Relative positioning means that the web developer specifies an X and Y offset from the usual position of the element. Fixed positioning means that the element is placed relative to the browser window, and scrolls with the window rather than with the rest of the page.{{cite web • The
CSS box model: This feature allows the web designer to specify dimensions, padding, borders, and margins,{{cite web •
CSS table formatting: This part of CSS allows the web designer to apply table formatting without traditional
HTML table markup. •
CSS generated content: Using CSS generated content, web developers can add decorations and annotations to specified elements without having to add the content to each one individually. •
CSS parsing: A number of illegal CSS statements are present in Acid2 to test error handling. Standards-compliant browsers are expected to handle these errors as the CSS specification directs. This helps ensure
cross-browser compatibility by making all browsers treat CSS with the same level of strictness, so that what works in one browser should not cause errors in another. •
Paint order: Acid2 requires that the browser has standard paint order. That is, overlapping elements should be placed or
painted on top of each other in the correct order. •
Hovering effects: When the user moves the mouse over the smiley face's nose, it turns blue. This is called a hovering effect, and while it has traditionally been used for
hyperlinks, it should work on a wide variety of HTML elements.{{cite web Because Acid2 is not a comprehensive test, it does not guarantee total conformance to any particular standard. A variant of the Acid2 test that does not test for data URI support is also available from the Web Standards Project. ==Test conditions==