System.Web.UI.WebControls.ListItemCollection.FindByText(string)' has some invalid arguments

I am using one dropdown list using following tag
<td height="35" class="ms-authoringcontrols" width="80%">  <asp:DropDownList ID="ddlStartTime" runat="server" class="ms-short"> <asp:ListItem Text="- Select Time -" Value="-1" Selected="True" /> <asp:ListItem Value="7.00"> 07:00 AM</asp:ListItem> <asp:ListItem Value="7.50"> 07:30 AM</asp:ListItem> <asp:ListItem Value="8.00"> 08:00 AM</asp:ListItem> <asp:ListItem Value="8.50"> 08:30 AM</asp:ListItem> <asp:ListItem Value="9.00"> 09:00 AM</asp:ListItem> ...