I am using master page and when I run this page, it shows the following error message:
a page can have only one server-side form tag
How can I solve this problem?
I think you did like this:
<asp:Content ID="Content2" ContentPlaceHolderID="MasterContent" runat="server">
<form id="form1" runat="server">
</form>
</asp:Content>
The form tag isn't needed. because you already have the same tag in the master page.
So you just remove that and it should be working.