Nullreferenceexception

<div class="main-content-agile">
			<div class="sub-main-w3">	
				<h2>Sign In</h2>
                <asp:Label ID="Sta" runat="server"></asp:Label>
				<form runat="server">
					<h6>Swiftly sign in with</h6>
					<div class="navbar-right social-icons"> 
						<a href="#" class="one-w3ls" ><i class="fa fa-facebook" aria-hidden="true"></i> Facebook</a>
						<a href="#" class="two-w3ls" ><i class="fa fa-google-plus" aria-hidden="true"></i>Google+</a>
						<div class="clear"></div>
					</div>
					<h6>Or use your email</h6>
					<div class="icon1">
						<input placeholder="Email" name="emailid" type="email" required="">
					</div>
					
					<div class="icon2">
						<input  placeholder="Password" name="Pass" type="password" required="">
					</div>
					<label class="anim">
					<input type="checkbox" class="checkbox">
						<span>Remember Me</span> 
						<a href="#">Forgot Password</a>
					</label> 
						<div class="clear"></div>
					<asp:Button ID="InsertButton" runat="server" Text="Submit" OnClick="insert"/>
				</form>
			</div>




my .cs code throwing nullreferenceexception



 protected void insert(object s, EventArgs e)
    {
        string email = Request.Form["emailid"];
        string password = Request.Form["pass"]; 
        try
        {
           
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["akshay.mdf"].ConnectionString);
            con.Open();
            String insertval = "INSERT INTO Table(email,password) VALUES(@email,@password)";
            SqlCommand cmd = new SqlCommand(insertval, con);

            cmd.Parameters.AddWithValue("@email", email);
            cmd.Parameters.AddWithValue("@password", password);
            cmd.ExecuteNonQuery();
            con.Close();
            Sta.Text = "Record Inserted Succesfully";
        }
        catch (Exception ex)
        {
            throw ex;
        }