You can use jQuery to do that. Try this in your header :
$(document).ready(function() {
$("#mymenu li:nth-child(3n+3)").addClass("last");
});
Note : for this to work you need to have enqueued jQuery.
You can use jQuery to do that. Try this in your header :
$(document).ready(function() {
$("#mymenu li:nth-child(3n+3)").addClass("last");
});
Note : for this to work you need to have enqueued jQuery.