Favicon Technical Information
Valid Code and Internet Explorer 6 and 7 Limitations
In 2006, when the new campus standards for the Web were first released, the code for the campus favicon did not meet W3.org standards for valid XHTML. This issue was examined before the standards were announced and a decision made to go with two lines of code to support most browsers.
One reason was because Internet Explorer 6, the dominant Web browser at the time (view W3Schools statistics), did not support PNG and GIF image file formats. For a while, the identity standards called for the end of the use of two lines of code and for the use of a .png file and this code: <link rel="icon" type="image/png" href="SOMEWHERE/favicon.png"> as W3.org indicated. However, while Firefox has made signficant market penetration gains and supports .png files, IE 7, which replaced IE 6, does not.
When IE 8, which at the time of this writing is in beta, is released it is expected that it will meet W3.org standards and support .png file formats. If so, the identity standards will revert to the W3.org standards for valid XHTML.
Those interested in more information are encouraged to read this Wikipedia article about favicons and also consult the Information Gift Web site, which has links to a chart with information about what browsers support favicons and what actions are supported and general favicon information.
Note that IE6 will activate a favorites icon only if you bookmark the site. A previously cached favicon may continue to appear. In IE 6, clicking on the favicon appearing in the address window and dragging it slightly, then releasing it (a kind of a jiggle) usually will cause the new favicon to appear.