You're not seeing any changes because you are replacing #Everything
with a clone of itself. The net effect is no change.
Instead, you can use the html function to set the contents of the #Everything
div:
var everything = $('#Everything');
$('#Select').change(function () {
var n = $(this).val();
switch (n) {
case '1':
everything.html("Hello from 1");
break;
case '2':
everything.html("Hello from 2");
break;
case '3':
everything.html("Hello from 3");
break
}
});