How to add a list item to an existing unordered list?

How about using "after" instead of "append".

$("#content ul li:last").after('<li><a href="/user/messages"><span class="tab">Message Center</span></a></li>');

".after()" can insert content, specified by the parameter, after each element in the set of matched elements.

You can also do it in a more 'object' and still easy-to-read way:

$('#content ul').append(
    $('<li>').append(
        $('<a>').attr('href','/user/messages').append(
            $('<span>').attr('class', 'tab').append("Message center")
)));

You don't have to fight with quotes then, but you must keep trace of braces :)

This would do it:

$("#header ul").append('<li><a href="/user/messages"><span class="tab">Message Center</span></a></li>');

Two things:

• You can just append the <li> to the <ul> itself.
• You need to use the opposite type of quotes than what you're using in your HTML. So since you're using double quotes in your attributes, surround the code with single quotes.

If you are simply adding text in that li, you can use:

 $("#ul").append($("<li>").text("Some Text."));