CSS selectors - how to select 'for' in CSS?

Using the (CSS2) attribute selector:

.error[for="username"]

This will work in IE8+ and all modern browsers.

---

IE7's attribute selector is buggy: as explained here, to match for you must use htmlFor.

So, if you need IE7 support, use this:

.error[for="username"], .error[htmlFor="username"]

In the css:

.error[for=username] {
}

In the jQuery

$('.error[for=username]')

Any attribute can be selected with CSS or jQuery using the [] notation. CSS applies to any XML-like syntax, not just HTML -- it doesn't know (or care) what attributes are "valid" as long as the structure is well-formed.

.error[for='username'] {

}

or for a "starts with"

.error[for^='userprefix'] {

}