Firefox 3.6 and 4 seems to ignore the noscript tag in certain cases even if scripting is enabled. I have pin-pointed this down to be a specific case only when the document is served as application/xhtml+xml. Firefox does not ignore the element completely, for example in <noscript><input type='submit' name='subn' value='NOSCRIPT SUBMIT' /></noscript> the submit button is NOT displayed. However this: <noscript><input type='hidden' name='nonjs' value='1' /></noscript> IS sent inside a POST form when document is served as application/xhtml+xml and NOT sent when it is served as text/html. I would like to ask if this is a normal and correct behavior, or if it is a bug. Opera and AFAIK ie does not send the hidden element in both cases. Chrome on the other hand, behaves exactly like firefox. I have prepared a test case, which can be accessed here: http://new.adina.sk/test.php USAGE: 1) luad the page and press SUBMIT 2) notice that the $_POST array printout contains the "nonjs" field set to 1, this is unexpected behavior. 3) click on the link "Serve as text/html; charset=utf-8" 4) again submit the form, this time notice the $_POST array printout does not contain the "nonjs" field. This is expected behavior. 5) you can switch between the two versions using links and submit data as wished I will be glad if someone could provide more information about this behavior. Thank you.