When I transfer my project to a server, I now get this error message. What does it mean and how do I fix it?

Server Error in '/HD' Application.

    Parser Error

    Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

    Parser Error Message: Could not load type 'HD._Default'.

    Source Error:


    Line 1:  <%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="HD._Default" %>
    Line 2:  
    Line 3:  <%@ Register Assembly="FormControls" Namespace="FormControls" TagPrefix="FC" %>

    Source File: /helpdeskform/HD/default.aspx    Line: 1