jquery ajax problem on IE and Firefox, but not Google Chrome.

jquery ajax problem on IE and Firefox, but not Google Chrome.

Hi,

I am having a problem where my IE (IE8) doesn't process a form using jquery ajax. Instead, it navigates to the target page (the page that receives the form data). I didn't want that. Okay, take a look at my code portion 

[base.js]

        function ExtConn()
{
this.getHTML = function(_url, querystring){
try{
bodyContent = $.ajax({
 url: _url,
 type: 'POST',
 data: querystring,
 async:false
});
//alert(bodyContent);
return bodyContent.responseText;
}catch(e){
return false;
}
};
this.sendForm = function(Form){
try{
$.post($(Form).attr('action'), $(Form).serialize()+"&do="+$(Form).attr('do'),
function(data){
data = $.trim(data);
if(data.indexOf("1")==0){
alert(data);
}else{
alert(data);
}
}
);
return false;
}catch(e){
return false;
}
};
}

[test.php]

if(isset($_POST['do'])){
$action = $_POST['do'];
}
switch($action){
case 'test':die(1);break;
default : die('ERROR');break;
}

okay with those two file, my page script looks like this :

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript" src="a/valid/path/to/jquery.js"></script>
<script type="text/javascript" src="base.js"></script>
<script type="text/javascript">
var page = new ExtConn();
</script>
</head>
<body>
<form name="myform" action="test.php" do="test" onsubmit="return page.sendForm(this);">
<input type="submit" value="Submit" />
</form>
</body>
</html>



in this case, when i clicked submit, my IE & firefox shows the test.php page with "ERROR!". I think it shouldn't be that way. And it supposed not to. 

Does someone know why this problem happen? And how do i fix it?

If you want to take a look at my scripts, i've attached it along with this post