Does anyone know how i make this form open in a new window when the submit button is clicked?

PHP Code:
<form method="post" action="http://www.gaybymail.com/subscriptions.html">
              <input type="text" name="email" size="30" maxlength="49" onfocus="this.value = ''" value="Enter your email address!"></td>
            <td valign="middle" align="center" width="91"><input type="submit" value="Subscribe" name="submit"></td>
            </form> 
Any help would be appreciated

Regards,

Lee