Problem with updatePanel and Javascript

<script type="text/javascript">
        function ToggleRowColor(element) {
            if (element.style.backgroundColor == 'cyan') {
                element.style.backgroundColor = '#5691da';
                element.style.cursor = 'hand';
                element.style.textDecoration = 'none';
            }
            else {
                element.style.backgroundColor = 'cyan';
                element.style.cursor = 'hand';
                element.style.textDecoration = 'underline';
            }
        }
    </script>

<asp:scriptmanager id="ScriptManager1" runat="server" xmlns:asp="#unknown">
    </asp:scriptmanager>
    <asp:updatepanel id="UpdatePanel1" runat="server" xmlns:asp="#unknown">
        <contenttemplate>
            <asp:gridview id="GridView1" runat="server" autogeneratecolumns="False" datakeynames="Subj_id">
                CssClass="cntrdatag" DataSourceID="SqlDataSource1" AllowPaging="True" AllowSorting="True"
                RowStyle-BackColor="#5691da" OnRowDataBound="GridView1_RowDataBound" OnRowUpdated="GridView1_RowUpdated"
                OnRowUpdating="GridView1_RowUpdating" OnRowDeleted="GridView1_RowDeleted" Font-Size="Large"
                Width="626px">
                <columns>
                    <asp:commandfield showeditbutton="True" showdeletebutton="True" headerstyle-width="180">
                        ButtonType="Button" ShowCancelButton="true"></asp:commandfield>
                    <asp:boundfield datafield="subj_id" headerstyle-backcolor="#08346b" headertext="Subject-ID">
                        SortExpression="subj_id" HeaderStyle-Width="100" ReadOnly="true">
                        <HeaderStyle BackColor="#08346b" Width="100px" ForeColor="White" BorderColor="Black">
                        </HeaderStyle>
                    </asp:boundfield>
                    <asp:boundfield datafield="subj_name" headerstyle-backcolor="#08346b" headertext="Subject-Name">
                        SortExpression="subj_name" HeaderStyle-Width="200">
                        <HeaderStyle BackColor="#08346b" Width="200px" ForeColor="White" BorderColor="Black">
                        </HeaderStyle>
                    </asp:boundfield>
                </columns>
                <pagertemplate>
                Current Page: <%=GridView1.PageIndex+1%>
                    Number of Pages:
                    <%=GridView1.PageCount %>
                    <br />
                    <asp:button id="btnFirst" runat="server" commandname="Page" cssclass="btn" commandargument="First">
                        Text="<<" />
                    <asp:button id="btnPrev" runat="server" commandname="Page" cssclass="btn" commandargument="Prev">
                        Text="<" />
                    <asp:button id="btnNext" runat="server" commandname="Page" cssclass="btn" commandargument="Next">
                        Text=">" />
                    <asp:button id="btnLast" runat="server" commandname="Page" cssclass="btn" commandargument="Last">
                        Text=">>" />
                </asp:button></asp:button></asp:button></asp:button></pagertemplate>
                <rowstyle backcolor="#5691da"></rowstyle>
            </asp:gridview>
        </contenttemplate>
    </asp:updatepanel>

</script>

protected void GridView1_RowUpdated(object sender, GridViewUpdatedEventArgs e)
    {
        if (e.Exception != null)
        {
            string x = e.Exception.Message; ;
            Response.Write(@"<script language='javascript'>alert('" + x + "');</script>");
        }
        else
        {
            Response.Write(@"<script language='javascript'>alert('Updated Successfully');</script>");
        }
    }