如何对齐（居中）行控件？

Question

我不知道如何将这些控件放在联系表格的中心位置，你能帮帮我吗？

以下是代码：

<div class="container">
                            <hr class="Tall" />
                            <div class="row center" id="form_contact">
                            <h2 class="short" style="text-align: center">Vamos <strong>Conversar</strong> ?</h2>
                            <p style="text-align: center">Queremos conhêce-lo melhor, descobrir quais são os seus problemas de modo a podermos ajudá-lo da melhor maneira possível.</p>
                                <div class="span12" id="form_fields">                   
                                    <form action="" id="contactForm" type="post">
                                        <div class="row controls">
                                            <div class="span3 control-group">
                                                <label>Nome *</label>
                                                <input type="text" value="" maxlength="100" class="span3" name="name" id="name">
                                            </div>
                                            <div class="span3 control-group">
                                                <label>Endereço de email *</label>
                                                <input type="email" value="" maxlength="100" class="span3" name="email" id="email">
                                            </div>
                                        </div>
                                        <div class="row controls">
                                            <div class="span6 control-group">
                                                <label>Assunto</label>
                                                <input type="text" value="" maxlength="100" class="span6" name="subject" id="subject">
                                            </div>
                                        </div>
                                        <div class="row controls">
                                            <div class="span6 control-group">
                                                <label>Mensagem *</label>
                                                <textarea maxlength="5000" rows="10" class="span6" name="message" id="message"></textarea>
                                            </div>
                                        </div>
                                        <div class="btn-toolbar">
                                            <input type="submit" value="Enviar" class="btn btn-primary btn-large" data-loading-text="Loading...">
                                        </div>
                                    </form>
                                </div>

                            </div>
                        </div>

https://jsfiddle.net/Ls4eLefh/

由于 -Nuno