In the following page, with Firefox the remove button submits the form, but the add button does not.
How do I prevent the remove
button from submitting the form?
You're using an HTML5 button element. Remember the reason is this button has a default behavior of submit, as stated in the W3 specification as seen here: W3C HTML5 Button
So you need to specify its type explicitly:
<button type="button">Button</button>
in order to override the default submit type. I just want to point out the reason why this happens.