I have 3 different function. If I remove the first one, then the code works (the second function). When I insert the first one, then it does not work. How do I fix this?

Code:
	$('#nav a').click(function() {
    	var index = $(this).index();
    	$('.panel').hide().eq(index).fadeIn();
    	return false;
	})​;
	
	
	$("#preview").change(function(){
            $("#previewPane")[ this.checked ? "show" : "hide"]();
			if(this.is(':checked')) { 
				$("#messagesContainer").css('height:400px'); 
			} ;
	}).change();