User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6) Gecko/20040206 Firefox/0.8 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6) Gecko/20040206 Firefox/0.8 Firefox will let users check/uncheck input elements of type checkbox/radio despite their specifying a proper readonly="readonly" attribute. Look at the page in bug's demo URL (XHTML 1.0 Strict): you can (un)check at will (except, of course, for radio mutual exclusion). Reproducible: Always Steps to Reproduce: This is demonstrated in the demo page mentioned in the URL field. 1. Create a form 2. Add an input element in it, say with type="checkbox", and make it readonly by adding readonly="readonly". 3. Load the page. Try (un)checking the box. Actual Results: The elements keep being modifiable. Expected Results: The checkbox/radio buttons should be unmodifiable (yet focusable). I didn't extend tests to other types of input or to textarea. I also didn't check it out on Mozilla itself, or other Gecko-based browsers.

"readonly" does not apply to checkboxes/radio buttons. See bug 88512 comment 14. *** This bug has been marked as a duplicate of 88512 ***

The misconception that "readonly" does not apply to checkboxes or radio buttons is based a misreading of a DTD comment. See the rest of the discussion at bug 88512.