Seems like related to IE issues, see this and related (sorry, can't post more than 2 links yet).
The first one will be fixed in next major IE release (Edge?).
The second one is still opened.
As I suspect, the problem is that user still can click into inputs inside disabled fieldset an edit them.
If so, there is "css only" workaround for IE 8+ that creates transparent overlay above disabled fieldset that prevents fieldset from being clicked.
The workaround is described in Microsoft Connect issues.
There is fiddle, that demonstrates workaround in action.
fieldset {
/* to set absolute position for :after content */
position: relative;
}
/* this will 'screen' all fieldset content from clicks */
fieldset[disabled]:after {
content: ' ';
position: absolute;
z-index: 1;
top: 0; right: 0; bottom: 0; left: 0;
/* i don't know... it was necessary to set background */
background: url( data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==);
}
The workaround has some limitations, see code for details.
There are some options with JavaScript.
Seems like for IE9+ you can catch mousedown events on fieldset and call e.preventDefault() if fieldset is disabled.
fieldset.onmousedown = function(e) {
if (!e) e = window.event;
if (fieldset.disabled) {
// for IE9+
if (e.preventDefault) {
e.preventDefault();
}
// for IE8-
else {
// actualy does not work
//e.returnValue = false;
}
return false;
}
}
For IE8 and below it is imposible to catch bubbling mousedown events on disabled fieldset, event handlers does not even gets called. But it is possible to catch them on fieldset ancestors, on documetn.body for exampe. But again, for IE8- you can't prevent element from being focused by preventing default action of mousedown event. See jQuery ticket #10345 for details (sorry, can't post more than 2 links). You can try to use UNSELECTABLE attribute to temporary forbid element to get focus. Something like this:
document.body.onmousedown = function(e) {
if (!e) e = window.event;
var target = e.target || e.srcElement;
if (fieldset.contains(target) && fieldset.disabled) {
// no need to do this on body!!! do it on fieldset itself
/*if (e.preventDefault) {
e.preventDefault();
}
else {*/
// this is useless
//e.returnValue = false;
// but this works
fieldset.setAttribute("UNSELECTABLE", "on");
window.setTimeout(function() { target.setAttribute("UNSELECTABLE", ""); },4);
/*}*/
return false;
}
}