checked before after defalut css code example
Example: checked radio button css
//html
<input id="rad1" type="radio" name="rad"/><label for="rad1">Radio 1</label>
<input id="rad2" type="radio" name="rad"/><label for="rad2">Radio 2</label>\
//css
input[type="radio"]:checked+label { font-weight: bold; }