Hi, after some painful debugging, I determined that there is a bug in the jQuery FAQs about how to clear a checkbox. Specifically, if you have a strict XHTML document, you *cannot* use .attr("checked","") to clear a checkbox. Instead, you must use .removeAttr("checked"). See the following PHP code sample:
<? header('Content-type: application/xhtml+xml'); print '<?xml version="1.0" encoding="iso-8859-1"?>' . "\n"; ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Checkbox test</title> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/ libs/jquery/1.3/jquery.min.js"></script> </head> <body> <p> <input type="checkbox" id="c"/> I'll be checked/unchecked. <input type="button" value="Check" onclick='$("#c").attr ("checked","checked")'/> <input type="button" value="Uncheck - fail" onclick='$("#c").attr ("checked","")'/> <input type="button" value="Uncheck - good" onclick='$("#c").removeAttr ("checked")'/> </p> </body> </html> I have updated the FAQ accordingly. Hope this helps.