How to add property to existing class

Question

I have got a CSS class like so:

.simpleClass {
    width: 25px;
}

And I have a matching element:

Answer 1

The stylesheet is defined in a file, and you can't edit that with JavaScript. What you could do is this:

$(".simpleClass").live("domchanged", function() {
    $(this).css("display", "none");
});

But this is neither not cross-browser compatible nor efficient (nor tested by me ;). So I'd propose to use another predefined CSS class for this purpose. Why do you need something like this anyway?