[jquery] Using an if statement to check if a div is empty

Try this:

$(document).ready(function() {
    if ($('#leftmenu').html() === "") {
        $('#menuTitleWrapper').remove();
        $('#middlemenu').css({'right' : '0', 'position' : 'absolute'});
        $('#PageContent').css({'top' : '30px', 'position' : 'relative'});
    }
});

It's not the prettiest, but it should work. It checks whether the innerHTML (the contents of #leftmenu) is an empty string (i.e. there's nothing inside of it).