Google Analytics and IE Browser

Question

Hi,

Anyone can explain me why below works in Firefox but not in IE.

function bookingSubmit(myform) {
 _gaq.push(['_linkByPost', myform, true]);
 return true;
}

<form id="booking-form" action="https://myurl.com" method="get" onsubmit="return bookingSubmit(this);">
<input type="text" name="whatever"/>
<input type="submit" name="Send"/>
</form>

Thanks!