Javascript not working when added masterpage

hi all Im tring to do Jquery autocomplete textbox with multiple words separated by comma .I got source code from this blog
http://www.aspdotnet-suresh.com/2012/07/jquery-autocomplete-textbox-with.html
But when tried to add master page to this page javascript not working or autofill not appearing.can anyone point out my mistake

<%@ Page Title="" Language="C#" MasterPageFile="~/Master.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
<link href="css/ui-lightness/jquery-ui-1.8.21.custom.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/jquery-ui.min.js"></script>
<script type="text/javascript">
$(document).ready(function () {
SearchText();
});
function SearchText() {
$("#txtSearch").autocomplete({
source: function (request, response) {
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "Default.aspx/GetAutoCompleteData",
data: "{'username':'" + extractLast(request.term) + "'}",
dataType: "json",
success: function (data) {
response(data.d);
},
error: function (result) {
alert("Error");
}
});
},
focus: function () {
// prevent value inserted on focus
return false;
},
select: function (event, ui) {
var terms = split(this.value);
// remove the current input
terms.pop();
// add the selected item
terms.push(ui.item.value);
// add placeholder to get the comma-and-space at the end
terms.push("");
this.value = terms.join(", ");
return false;
}
});
$("#txtSearch").bind("keydown", function (event) {
if (event.keyCode === $.ui.keyCode.TAB &&
$(this).data("autocomplete").menu.active) {
event.preventDefault();
}
})
function split(val) {
return val.split(/,\s*/);
}
function extractLast(term) {
return split(term).pop();
}
}
</script>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

<div class="demo">
<div class="ui-widget">
<label for="tbAuto">Enter UserName: </label>
<%--<input type="text" id="txtSearch" />--%>
<asp:TextBox ID="txtSearch" runat="server" Width="300px"></asp:TextBox>
</div>
</div>
</asp:Content>

Thanks in Advance

thanks and regards
Amrutha