How to open this document in the web-based application and get the count of hits on it?

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C#

ASP.NET

SQL-Server

I am a new ASP.NET developer and I am trying to develop a page called Useful Library that will contain many things such as useful presentations and pdf documents. I have a folder in the Server called (Useful Resources) and I put all those useful presentations and documents in it. I have the following table in my database:

UsefulResources Table: ID, Category, Title, URL, Uploaded Date, Hits

The reason of designing this table is to organize the resources and count the hits on the link of the document. I implemented it and it shows well in the page. However, when I click on one of the links, I got the following error and I don't know why:
404 - File or directory not found.
The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.

The clicked link will be like this:
http://www.pmvt.com/msa/pssp/UsefulResourcesCountHits.asp?ID=1&link=Useful%20Resources/Electrical%20safety.ppt[^]

**Could you please help me in this?**

My ASP.NET Code:

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
        DataSourceID="Sql_Categories" ShowHeader="False" Width="100%"
        BorderStyle="None" GridLines="None">
        <Columns>
            <asp:TemplateField HeaderText="Category" SortExpression="Category">
                <ItemTemplate>
                <a id='<%# (Eval("Category").ToString()) %>'> </a>
                <br />
                    <asp:Label ID="Label1" runat="server" Text='<%# Eval("Category") %>'
                        style="font-weight: bold; font-size: 14px"></asp:Label>
                <br />
                    <asp:SqlDataSource ID="Sql_Reports" runat="server"
                        ConnectionString="<%$ ConnectionStrings:testConnectionString %>"
                        SelectCommand="SELECT [ID], [Title], [URL], [UploadedDate] FROM [UsefulResources] WHERE ([Category] = @Category) ORDER BY [UploadedDate] DESC">
                        <SelectParameters>
                            <asp:ControlParameter ControlID="Label1" Name="Category" PropertyName="Text"
                                Type="String" />
                        </SelectParameters>
                    </asp:SqlDataSource>
                    <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False"
                        CellPadding="4" DataSourceID="Sql_Reports" ForeColor="#333333" GridLines="None"
                        Width="100%">
                        <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
                        <RowStyle BackColor="#E3EAEB" />
                        <Columns>
                            <asp:BoundField DataField="Title" HeaderText="Title" SortExpression="Title">
                                <ItemStyle HorizontalAlign="Center" Wrap="False" Width="100px" />
                            </asp:BoundField>
                            <asp:HyperLinkField DataNavigateUrlFields="ID,URL"
                                DataNavigateUrlFormatString="Useful Resources/UsefulResourcesCountHits.asp?ID={0}&link=Useful Resources/{1}"
                                DataTextField="Title" HeaderText="Title" />
                            <asp:BoundField DataField="UploadedDate" DataFormatString="{0:MMM yyy}" HeaderText="UploadedDate"
                                SortExpression="UploadedDate">
                                <ItemStyle HorizontalAlign="Center" Wrap="False" Width="100px" />
                            </asp:BoundField>
                        </Columns>
                        <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" />
                        <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" />
                        <HeaderStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
                        <EditRowStyle BackColor="#7C6F57" />
                        <AlternatingRowStyle BackColor="White" />
                    </asp:GridView>
                <div align="right"><a href='#Top'>Back to Categories</a></div>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <asp:SqlDataSource ID="Sql_Categories" runat="server"
        ConnectionString="<%$ ConnectionStrings:testConnectionString %>"

                SelectCommand="SELECT DISTINCT [Category] FROM [UsefulResources]">
    </asp:SqlDataSource>