SO fiddle

Test Fiddle mainly for SO Questions

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<div id='main_container'>
    <div id="container">
        <div class="wrapper">
            <div><label>... </label></div>
            <div><input type="text" id="one" new="one_1" /></div>
        </div>
        <div class="wrapper">
            <div><label>... </label></div>
            <div>
                <select id="two" new="two_1" >
                    <option>...</option>
                    <option>...</option>
                </select>
            </div>
        </div>
        <div class="wrapper">
            <div><label>... </label></div>
            <div>
                <select id="three" new="three_1" >
                    <option>...</option>
                    <option>...</option>
                </select>
            </div>
        </div>
    </div>

    <div class="wrapper">
        <input type="button" value="add a section" id="button" />
    </div>
</div>

CSS

.one { width: 200px; }
.two { width: 300px; }
.three { width: 400px; }

JavaScript

$('#button').click(function(){
    var clone = $('#container').clone().appendTo('#main_container');
    clone.find('[new*="one"]').attr('class', 'one');
    clone.find('[new*="two"]').attr('class', 'two');
    clone.find('[new*="three"]').attr('class', 'three');
    clone.find('[id]').removeAttr('id');
});