If you have ever accessibly styled a checkbox/radio button using the :checked pseudo-selector, you know that IE8- don't support it. We usually have two options: either a custom Modernizr test or either a conditional IE class.
There's a simpler way to detect it and it doesn't rely on anything external:
/* hide the default element only on browsers that support :checked */
input:checked, input:not(checked) {
display: none;
}
/* now you're free to style the label and IE8- will still have the original one */
input:checked + label {
...
}