Tak jest:
<form name="formular" action="" method="post" onsubmit="changeAction('login');">
A musi być tak:
<form id="formular" action="" method="post" onsubmit="changeAction('login');">
Dzieki za pomoc
ROZWIĄZANE : document.forms['formular']

<form name="formular" action="" method="post" onsubmit="changeAction('login');">
<form id="formular" action="" method="post" onsubmit="changeAction('login');">