Javascript Validation along with fileupload control

<script type="text/javascript">
    function ValidSubmit()
    {
       var Franchise = document.getElementById('ContentPlaceHolder1_cbox_Franchisewise');
       if (Franchise.checked)
      {
       } //For Radiobutton or checkbox validation
   if (document.getElementById('<%=ddlcomplaintabout.ClientID%>').selectedIndex == 0) {
       alert("Please select the item from dropdown");
       return false;
   }
        if (document.getElementById('ctl00_ContentBody_txt_ClippingTitle').value == '')
        {
            alert("Please Enter Title");
            return false;
        }

Get RadioButtonlist Selected Value

 var radioButtonlist = document.getElementById("<%#rbtnlst_Sector.ClientID%>");
            var radio = radioButtonlist.getElementsByTagName("input");
            for (var x = 0; x < radio.length; x++)
            {
                if (radio[x].type === "radio" && radio[x].checked)
                {
                    NATURE_SMS= radio[x].value;
                }
            }


For RadiobuttonList 
 var r = document.getElementsByName("RadioButtonList_MNTF")
            var c = -1

            for (var i = 0; i < r.length; i++)
            {
                if (r[i].checked)
                {
                    c = i;
                }
            }
            if (c == -1)
             {
                alert("please select radio");
                return false;
            }
        if (document.getElementById('<%= BtnInsert.ClientID %>').value == 'Submit')
         {
             var fup = document.getElementById('<%= fileUplaod_ClippingImage.ClientID %>');
             var fileName = fup.value;
             if (fileName == "")
            {
                alert("Please attach image");
                return false;
            }
            else
            {
                var ext = fileName.substring(fileName.lastIndexOf('.') + 1);
                if (ext == "gif" || ext == "GIF" || ext == "JPEG" || ext == "jpeg" || ext == "jpg" || ext == "JPG" || ext == "png" || ext == "PNG") {

                    //now check size height/width
                    return true;
                }
                else {
                    alert("Please Upload an Image File");
                    //document.getElementById('<%= Upload_Symptoms.ClientID %>').value = '';
                    fup.focus();
                    return false;
                }
            }
        }


    }
 
    </script>

Call the function on OnClientClick event of Button

<asp:Button CssClass="Details" ID="BtnInsert" runat="server" Text="Submit"
onclick="BtnInsert_Click" OnClientClick="return ValidSubmit();"
style="height: 21px" />

Gridview Formatting with Paging

css
--------------------------------------------------
<style type="text/css" media="screen">

    .pager a
    {
            border: 1px solid #EDF5FF;
            color: #0067A5;
            text-decoration: underline;
            padding: 2px 5px;
    }
    .pager span
    {
            background-color: #0067A5;
            border: 1px solid #DBEAFF;
            color: #FFFFFF;
            padding: 2px 5px;
    }
    .pager a:hover
    {
        color: #1E90FF;
    }


    </style>

Inside body
-----------------------------------------------
<asp:GridView ID="GridCourse" runat="server" AutoGenerateColumns="false"
 Width="100%" GridLines="None" ShowHeader="true"
ShowFooter="false" onpageindexchanging="GridCourse_PageIndexChanging"
onrowdatabound="GridCourse_RowDataBound" AllowPaging="true" PageSize="10" >
<Columns>  

<asp:TemplateField HeaderText="SNo">
<HeaderStyle CssClass="DetailsContent" />
<ItemStyle Width="5%" Height="18px"  HorizontalAlign="Center" CssClass="DetailsContent"></ItemStyle>
<ItemTemplate>                      
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Title">
<HeaderStyle CssClass="DetailsContent" />
<ItemTemplate>
<asp:Label ID="lbl_title" runat="server" Text='<%#Eval("Clipping_Title")%>'></asp:Label>
</ItemTemplate>
<ItemStyle Width="30%" Height="18px"  HorizontalAlign="Center" CssClass="DetailsContent"></ItemStyle>
</asp:TemplateField>
<asp:TemplateField HeaderText="Clipping Image">
<HeaderStyle CssClass="DetailsContent" />
<ItemTemplate>
<asp:Image ID="Img_Clipping" runat="server" Height="50px" Width="50px" ImageUrl='<%#"../NewsClippings/"+Eval("Clipping_ImagePath")+"" %>' />
</ItemTemplate>

<ItemStyle Width="25%" Height="18px"  HorizontalAlign="Center" CssClass="DetailsContent"></ItemStyle>
</asp:TemplateField>
<asp:BoundField HeaderText="Posted On" DataField="Upload_On" DataFormatString="{0:d}">
<HeaderStyle  CssClass="DetailsContent"/>
<ItemStyle Width="20%"  HorizontalAlign="Center" CssClass="DetailsContent"/>
</asp:BoundField>
<asp:TemplateField HeaderText="Action">
<HeaderStyle CssClass="DetailsContent" />
<ItemTemplate>
<asp:LinkButton ID="lbtn_Edit" CssClass="Details" runat="server" Text="Edit" CommandName="Edit" CommandArgument='<%#Eval("Clipping_Id") %>'></asp:LinkButton>
<asp:LinkButton ID="lbtn_Delete" CssClass="Details" runat="server" Text="Delete" CommandName="Delete" CommandArgument='<%#Eval("Clipping_Id") %>'></asp:LinkButton>
</ItemTemplate>
<ItemStyle Width="20%" Height="18px"  HorizontalAlign="Center" CssClass="DetailsContent"></ItemStyle>
</asp:TemplateField>
</Columns>  
<HeaderStyle BackColor="Silver" Height="20px" />  
 <PagerStyle HorizontalAlign="Right" CssClass="pager"/>
   
</asp:GridView>


In code
-----------------------------------
 protected void grd_ExistingImage_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        grd_ExistingImage.PageIndex = e.NewPageIndex;    
        int id = bindAvailableCategory(CategoryName);
        bindImagestoGridview(id);
    }