VS 2010 HTTPWebRequest Post Data Javascript

Hello guys, just wanna ask you guys about
"How to create a webrequest with Java Script"

i have tried using the httpliveheaders but i cannot see a post data of it coz its all a plain javascript >.<
i have tried figuring out but i really cannot sort it out.

below this code is the page source of a certain site.
vb Code:
<html>
<head>
<title>Login</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<script language="JavaScript" src="../../index.res"></script>
<script language="JavaScript" src="../js/util.js"></script>
<style type="text/css">
a
{
color:#FFFFFF;
cursor:hand;
font-family:Arial;
font-size:14px;
font-weight:bold;
text-decoration :none;
}
b
{
color:blue;
cursor:hand;
font-family:Arial;
font-size:14px;
font-weight:bold;
text-decoration :none;
}
td
{
font-family:Arial;
font-size:14px;
}
a:hover {
color: blue;
}
b:hover {
color: blue;
}
body
{
margin: 0 0 0 0;
font-family:Arial;
}
</style>
<script language="JavaScript" type="text/javascript">
var checkFocusValue = 0;
var curProductClass = "6";  // 0--BM625  1--BM635
var LoginTimes = 0;
var Cookieflag = 0;
var inittime = 0;
var initcount = 0;
var firmenu = 'Admin_0';
var secmenu = 'Admin_0_0';
var thirdmenu = 'Admin_0_0_0';
var strCookie = document.cookie;
var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var base64DecodeChars = new Array(
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);
function base64encode(str) {
var out, i, len;
var c1, c2, c3;
len = str.length;
i = 0;
out = "";
while(i < len) {
c1 = str.charCodeAt(i++) & 0xff;
if(i == len)
{
out += base64EncodeChars.charAt(c1 >> 2);
out += base64EncodeChars.charAt((c1 & 0x3) << 4);
out += "==";
break;
}
c2 = str.charCodeAt(i++);
if(i == len)
{
out += base64EncodeChars.charAt(c1 >> 2);
out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
out += base64EncodeChars.charAt((c2 & 0xF) << 2);
out += "=";
break;
}
c3 = str.charCodeAt(i++);
out += base64EncodeChars.charAt(c1 >> 2);
out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6));
out += base64EncodeChars.charAt(c3 & 0x3F);
}
return out;
}
function base64decode(str) {
var c1, c2, c3, c4;
var i, len, out;
len = str.length;
i = 0;
out = "";
while(i < len) {
/* c1 */
do {
c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
} while(i < len && c1 == -1);
if(c1 == -1)
break;
/* c2 */
do {
c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
} while(i < len && c2 == -1);
if(c2 == -1)
break;
out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));
/* c3 */
do {
c3 = str.charCodeAt(i++) & 0xff;
if(c3 == 61)
return out;
c3 = base64DecodeChars[c3];
} while(i < len && c3 == -1);
if(c3 == -1)
break;
out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
/* c4 */
do {
c4 = str.charCodeAt(i++) & 0xff;
if(c4 == 61)
return out;
c4 = base64DecodeChars[c4];
} while(i < len && c4 == -1);
if(c4 == -1)
break;
out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
}
return out;
}
function SubmitForm()
{
var usernamevalue;
var passwordvalue;
var Username = document.getElementById('txt_Username');
var Password = document.getElementById('txt_Password');
usernamevalue = Username.value;
passwordvalue = Password.value;
if (Username.value == "")
{
alert(eval("gErrStr0"));
return false;
}
if (usernamevalue.length > 31)
{
alert(eval("gErrStr7"));
return false;
}
if(!isValidName(usernamevalue))
{
alert(eval("gErrStr8"));
return false;
}
if (Password.value == "")
{
alert(eval("gErrStr1"));
return false;
}
if (passwordvalue.length > 31)
{
alert(eval("gErrStr9"));
return false;
}
if(!isValidName(passwordvalue))
{
alert(eval("gErrStr10"));
return false;
}
if (document.cookie == '')
{
var cookie = "LoginTimes=" + initcount + ":" +  "LoginOverTime=" + inittime + "; path=/";
document.cookie = cookie;
}
var cookie = "FirstMenu=" + firmenu + "; path=/";
document.cookie = cookie;
var cookie = "SecondMenu=" + secmenu + "; path=/";
document.cookie = cookie;
var cookie = "ThirdMenu=" + thirdmenu + "; path=/";
document.cookie = cookie;
var form = new webSubmitForm();
form.setAction('login.cgi?Username='+ Username.value + '&Password=' + base64encode(Password.value) + '&RequestFile=html/content.asp');
form.submit();
return true;
}
function LoadFrame()
{
hideContextmenu();
document.getElementById('txt_Username').tabIndex = 1;
document.getElementById('txt_Password').tabIndex = 2;
document.getElementById('btnLogin').tabIndex = 3;
document.getElementById('btnCancel').tabIndex = 4;
document.getElementById('txt_Username').focus();
if (getElement("lang_2").value == "" || getElement("lang_2").value == null || getElement("lang_2").value == undefined)
{
setDisplay("lang_1", 0);
}
}
function onCancel()
{
if (true == confirm(eval("gErrStr5")))
{
var Username = document.getElementById('txt_Username');
var Password = document.getElementById('txt_Password');
Username.value = '';
Password.value = '';
}
else
{
}
}
function checkFocus(value)
{
checkFocusValue = value;
}
function onHandleKeyDown(e)
{
if (e.keyCode == 13)
{
if((checkFocusValue == 1)||(checkFocusValue == 2))
{
SubmitForm();
}
}
}
function websetlang(langtype)
{
var form = new webSubmitForm();
form.setAction('language.cgi?Language='+ langtype + '&RequestFile=html/index.asp');
form.submit();
}
</script>
</head>
<!--  rightmargin="0" leftmargin="0" bottommargin="0" topmargin="0" marginheight="0" marginwidth="0"    <input type="button" value="Login" style="width:200px;height:24px; background-image:../../images/btninit.gif;"><div style="position:relative;left:150px;top:100px"></div>-->
<body onLoad="LoadFrame();">
<div id="LoginForm" action="/login.cgi" method="get" onkeydown='return onHandleKeyDown(event);'>
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
<tr>
<td height="61" valign="top">
<table width="100%" border="0" cellpadding="0" cellspacing="0" height="100%">
<tr>
<td width="16%" height="68">
<table width="100%" border="0" cellpadding="0" cellspacing="0" height="100%" background="../../images/logoback.gif" >
<tr>
<td align="center"> <img src="../../images/logo.gif"   border="0" style="position:relative; top:0px"></img> </td>
</tr>
</table>
</td>
<td width="1%" background="../../images/leftblock.gif">&nbsp;</td>
<td background="../../images/midblock.gif" valign="top">
<table height="61" border="0">
<tr>
<td height="26" colspan="5"></td>
</tr>
<tr>
<td width="30" height="27">&nbsp;</td>
<td width="504" valign="top">
<b>
<font color="#006699" style="font-family:Arial;font-size:16px;">
<script language="JavaScript" type="text/javascript">
if(curProductClass == '0')
{
document.write("EchoLife BM625 WiMAX CPE");
}
else if(curProductClass == '1')
{
document.write("EchoLife BM635 WiMAX CPE");
}
else if(curProductClass == '2')
{
document.write("EchoLife BM626 WiMAX CPE");
}
else if(curProductClass == '3')
{
document.write("EchoLife BM632 WiMAX CPE");
}
else if(curProductClass == '4')
{
document.write("EchoLife BM631a WiMAX CPE");
}
else if(curProductClass == '5')
{
document.write("EchoLife BM655 WiMAX CPE");
}
else if(curProductClass == '6')
{
document.write("EchoLife BM622 WiMAX CPE");
}
else if(curProductClass == '7')
{
document.write("HUAWEI BM632w WiMAX CPE");
}
else if(curProductClass == '8')
{
document.write("HUAWEI BM652 WiMAX CPE");
}
else
{
document.write("HUAWEI UNKNOWN WiMAX CPE");
}
</script>
</font>
<b>
</td>
<td width="117" valign="top">&nbsp;</td>
<td width="70" valign="top">
<b value='English' id="lang_1" name="lang_1" onclick="websetlang(getElement('lang_1').value)">
English
</b>&nbsp;&nbsp;&nbsp;
</td>
<td width="70" valign="top">
<b value='' id="lang_2" name="lang_2" onclick="websetlang(getElement('lang_2').value)">
 
</b>&nbsp;&nbsp;&nbsp;
</td>
<td width="70" valign="top">
<b value='' id="lang_3" name="lang_3" onclick="websetlang(getElement('lang_3').value)">
 
</b>&nbsp;&nbsp;&nbsp;
</td>
</tr>
<script language="JavaScript" type="text/javascript">
if (getElement("lang_2").value == "" || getElement("lang_2").value == null || getElement("lang_2").value == undefined)
{
setDisplay("lang_1", 0);
}
</script>
<tr> </tr>
</table>
</td>
<td width="1%" background="../../images/rightblock.gif">&nbsp;</td>
</tr>
</table>
</td>
</tr>
<tr>
<td height="510" background="../../images/loginbackground.gif" align="center">
<table height="196" width="292" cellpadding="0" cellspacing="0" border="0" style="position:relative;top:-70px;">
<tr>
<td>
<table height="195" width="420" cellpadding="0" cellspacing="0" border="0">
<tr>
<td width="6" background="../../images/loginleft.gif" ></td>
<td width="403" background="../../images/loginmid.gif">
<table width="83%" height="101" border="0" cellpadding="0" cellspacing="0">
<tr><td height="40">&nbsp;</td></tr>
<tr  class="trTabConfigure">
<td width="136" align="right"><script language="JavaScript" type="text/javascript">document.write(eval("gVarUsername"));</script></td>
<td width="221" align="center">
<input style="height:22px; font-family:Arial;" id="txt_Username" type="text" name="Username" onfocus="checkFocus(1);">
</td>
</tr>
<tr><td height="20"></td></tr>
<tr  class="trTabConfigure">
<td align="right"><script language="JavaScript" type="text/javascript">document.write(eval("gVarPassword"));</script></td>
<td align="center">
<input style="height:22px; font-family:Arial;" id="txt_Password" name="Password" type="password" onfocus="checkFocus(2);">
</td>
</tr>
<tr><td height="20"></td></tr>
<!--
<tr  class="trTabConfigure">
<td align="right"><script language="JavaScript" type="text/javascript">document.write(eval("gVarLanguage"));</script></td>
<td align="center">
<select name="Language" size='1' id="Language" onChange=""  style="width: 155px; height:22px;">
<option value="0" selected> English </option>
<option value="1"> 中文 </option>
</select>
</td>
</tr>
-->
</table>
<table width="402" height="45" border="0"  cellpadding="0" cellspacing="0">
<tr>
<td height="13"> </td>
<td colspan="2"> </td>
</tr>
<tr>
<td width="71" height="32" align="right"> <img src="../../images/sigh.gif"></img></td>
<td width="6" align="left"></td>
<td width="325" align="left">
<script language="JavaScript" type="text/javascript">
if (LoginTimes == 0)
{
document.write('<font color="#0000FF">'+eval("gErrStr2"))
}
else if (LoginTimes == 1)
{
document.write('<font color="#FF3300">'+eval("gErrStr3"))
}
else if (LoginTimes == 2)
{
document.write('<font color="#FF3300">'+eval("gErrStr6"))
}
else if (LoginTimes >= 3)
{
document.write('<font color="#FF3300">'+eval("gErrStr4"))
}
</script>
</font> </td>
</tr>
</table>
</td>
<td width="7" background="../../images/loginright.gif" ></td>
</tr>
</table>
</td>
</tr>
<tr>
<td>
<table height="30" width="100%" cellpadding="0" cellspacing="0" border="1" style="border-color:#efefef;">
<tr>
<td width="217" background="../../images/btninit.gif" align="center"><a id="btnLogin" href="#" onfocus="checkFocus(3);" onClick="SubmitForm();">
<script language="JavaScript" type="text/javascript">document.write(eval("gVarLogin"));</script></a></td>
<td width="197" align="center" background="../../images/btninit.gif"><a id="btnCancel" href="#" onfocus="checkFocus(4);" onClick="onCancel();">
<script language="JavaScript" type="text/javascript">document.write(eval("gVarCancal"));</script>
</a></td>
</tr>
</table>
</td>
</tr>
</table>
</td>
</tr>
<tr>
<td style="background-color:#d1d1d1" valign="bottom"></td>
</tr>
</table>
</div>
</body>
</html>
can anyone help me out how to login by triggering the Javascripts of it.

Really appreciate if someone would help me out. Thanks!