为什么这些<；表单>'；s不被FF和Chrome识别

我有一些PHP逻辑呈现的以下表单。形式呈现精细；您可以看到文本输入和提交按钮等等。

在IE中，表单按预期运行。第一个表单转到"index.php"？subscribe=go，第二个到index.php？unsob=go'，但在FF和Chrome中，单击提交按钮会重新加载页面（不进入表单操作）。我没有检查过其他浏览器。

我在Firebug中发现<form>标签在Firefox的页面上甚至不存在。这很奇怪；查看：

else
    {
        echo '<div class="subs_main">';
        if (isset($_GET['subscribe']))
        {
            if ($_GET['subscribe'] != 'go')
            {?>
                Subscribe to <b>Bella Blog</b> for specials, sales, news and more!
                <br />
                <form action="index.php?subscribe=go" method="post" name="subscribe_form" onsubmit="return checkForm();">
                Name: <input type="text" name="name" size="15" />
                <br />
                Email: <input type="email" name="email" size="20" />
                <br />
                <input type="submit" value="subscribe!" name="submit" />
                </form>
                <p class="unsub">You can <a href="index.php?unsub">unsubscribe</a> at any time</p>
            <?php
            } 
            else
            {
                // subscribe user
            }
        }
        elseif (isset($_GET['unsub']))
        {
            if ($_GET['unsub'] != 'go')
            {?>
                Sorry to see you go! You can <a href="index.php?subscribe">re-subscribe</a> at any time!
                <br />
                <form onsubmit="return checkForm2()" name="unsub_form" method="post" action="index.php?unsub=go">
                Email: <input type="email" name="email" size="20" />
                <br />
                <input type="submit" value="unsubscribe" name="submit" />
                </form>
            <?php 
            }
            else
            {
                // process unsubscription HERE
            }
        }
        echo '</div>';
    }

这是用于表单验证的JS（我认为可以忽略不计，因为它在IE中有效，并且我在注释这个脚本时得到了相同的结果）：

<script type="text/javascript" language="javascript">
function checkForm()
{
    var regex = /^[a-zA-Z0-9._-]+@[a-zA-Z0-9.-]+'.[a-zA-Z]{2,6}$/;
    var form = document.forms.subscribe_form;
    var name = form.name.value;
    var email = form.email.value;
    if (name == '' || email == '')
    {
        alert('You must enter both your name and email address!');
        return false;
    }
    else if (!email.match(regex))
    {
        alert('You must enter a valid email!');
        return false;
    }
    return true;
}
function checkForm2()
{
    var form = document.forms.unsub_form;
    var email = form.email.value;
    if (email == '')
    {
        alert('You must enter an email address!');
        return false;
    }
    return true;
}
</script>