为什么PHP会破坏我的CSS？

I have recently created a contact form with PHP mailer which is finally working. However the success message is breaking my page and displaying in the top left corner instead of underneath the form. As you can see below.

This is the HTML:

<form method="POST">
       <table border="1">
            <tr>
            <td><label for="name" class="g">Name</label></td>
            <td><input id="name" name="name" type="text" autofocus></td>
            </tr>

            <tr>
            <td><label for="address" class="g">Address</label></td>
            <td><textarea rows="3" id="address" name="address" cols="50"></textarea></td>
            </tr>

            <tr>
            <td><label for="number" class="g">Contact number</label></td>
            <td><input id="number" name="number" type="text" autofocus></td>
            </tr>

            <tr>
            <td><label for="email" class="g">Email</label></td>
            <td><input id="email" name="email" type="text" placeholder="example@domain.com" autofocus></td>
            </tr>

            <tr>
            <td><label for="message" class="g">Enquiry</label></td>
            <td><textarea rows="3" id="message" name="message" cols="50"></textarea></td>
            </tr>
            </table>
            <input type="submit" value="Submit" name="submit">
            <?php
            if ($success) {
                echo $success;
            }
            ?>

            </form>

It also creates a huge blank white area in the middle of my page under the form. Does anyone know why this is? or how I would go about debugging it?

You should put this in a div or a span

<div style="text-align:center;"> <?php
        if ($success) {
            echo $success;
        }
        ?>
</div>

Try following code:

 <form method="POST">
   <table border="1">
        <tr>
        <td><label for="name" class="g">Name</label></td>
        <td><input id="name" name="name" type="text" autofocus></td>
        </tr>

        <tr>
        <td><label for="address" class="g">Address</label></td>
        <td><textarea rows="3" id="address" name="address" cols="50"></textarea></td>
        </tr>

        <tr>
        <td><label for="number" class="g">Contact number</label></td>
        <td><input id="number" name="number" type="text" autofocus></td>
        </tr>

        <tr>
        <td><label for="email" class="g">Email</label></td>
        <td><input id="email" name="email" type="text" placeholder="example@domain.com" autofocus></td>
        </tr>

        <tr>
        <td><label for="message" class="g">Enquiry</label></td>
        <td><textarea rows="3" id="message" name="message" cols="50"></textarea></td>
        </tr>
        <?php
        if ($success) {?>

            <tr><td colspan="2">

            <?php echo $success; ?>
           </td></tr>
        <?php }
        ?>
        </table>
        <input type="submit" value="Submit" name="submit">

        </form>