WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for ‘jquery’. Please add a ScriptResourceMapping named jquery(case-sensitive)

I’m building a web application using Visual Studio 2012.
I’m attempting to add word count into my textbox.
However after adding the the javascript codes and the html codes. I receive the error as stated above.

Here is my javascript codeds

Code :

function validateLimit(obj, divID, maxchar) {

objDiv = get_object(divID);

if (this.id) obj = this;

var remaningChar = maxchar - trimEnter(obj.value).length;

if (objDiv.id) {
    objDiv.innerHTML = remaningChar + " characters left";
}
if (remaningChar <= 0) {
    obj.value = obj.value.substring(maxchar, 0);
    if (objDiv.id) {
        objDiv.innerHTML = "0 characters left";
    }
    return false;
}
else
{ return true; }
}

function get_object(id) {
var object = null;
if (document.layers) {
    object = document.layers[id];
} else if (document.all) {
    object = document.all[id];
} else if (document.getElementById) {
    object = document.getElementById(id);
}
return object;
}

function trimEnter(dataStr) {
return dataStr.replace(/(\r\n|\r|\n)/g, "");
}

Server codes in master page

<script type="text/javascript" src="https://stackoverflow.com/questions/16660900/js/JScript.js" ></script>

ASPX codes, ( Html codes )

<tr>
<th style="width: 595px; height: 135px;">Official Report :</th>
<td colspan="4" style="height: 135px">
  <asp:TextBox ID="tbofficial" runat="server" Height="121px" TextMode="MultiLine" Width="878px" MaxLength="500"   ToolTip="Summary:(500 characters)" onkeyup="return validateLimit(this, 'lblMsg1', 500)" ></asp:TextBox>
  <div id="lblMsg1">500 characters left</div>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" 
        ControlToValidate="tbofficial" Display="Dynamic" 
        SetFocusOnError="True">*</asp:RequiredFieldValidator>
  <br />
  <asp:Label ID="lblmsg" runat="server"></asp:Label>
  <br />
  <br />
        <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" />
  <asp:Button ID="btnClear" runat="server" Text="Clear" OnClick="btnClear_Click" />
        </td>
</tr>