Use document.forms[0].SUBMIT(); (0 REFERS to the index of the FORM – if you have more than one form in a page, then the first one has the index 0, second has index 1 and so on).
Use document.forms[0].submit(); (0 refers to the index of the form – if you have more than one form in a page, then the first one has the index 0, second has index 1 and so on).