Form Submission Opens New Tab/Window
You probably knew that you could force a link into opening a new tab or window with the target="_blank" attribute (deprecated, but universally still supported).
<a href="#" target="_blank">link</a>
But you can use the same exact attribute on forms to get the same result:
<form action="#" method="post" target="_blank">
*May or may not contain any actual "CSS" or "Tricks".