jsp登录检测的500-错误

我做的jsp登录页面
<%@ page language="java" import="java.util.*,java.sql.*" pageEncoding="GB2312"%>
<html>
  <head>   
       
</head>
 <body>
  <center><h1>管理员登陆</h1></center><BR/>
  
    <form name="f1" id="f1" action="guanliyuanjiance.jsp" method="post">
      <table border="0" align=center>
        <tr>
          <td>用户:</td>
          <td>
          <input type="text" name="username" id="username" value=""></td>
        </tr>
        <tr>
          <td>密码:</td>
          <td>
          <input type="passwd" name="passwd" id="passwd" value=""></td>
        </tr> 
        <tr>
          <td colspan="2" align="center">
          <input type="submit" value="登陆"></td>
        </tr>
      
      </table>
      <table align="center">
    <a href="index.jsp">返回首页</font></a>
      
      </table>
    </form>
  </body>
  
</html>
检测页面
<%@ page language="java" import="java.util.*,java.sql.*" pageEncoding="gb2312"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'guanliyuanjiance.jsp' starting page</title>
    
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">    
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->  </head>
  
  <body>
  <%
    String a=request.getParameter("username");
    String b=request.getParameter("passwd");
    %>
    <%
    //1,加载驱动 
    Class.forName("com.microsoft.jdbc.sqlserver.SqlServerDriver");
    //2，得到连接 
    Connection conn=DriverManager.getConnection("jdbc:microsoft:sqlserver://localhost;DatabaseName=userdb","jie","123");
    //3，创建Statement
   Statement stmt=conn.createStatement();
  //4,查询 
  ResultSet rs=stmt.executeQuery("SELECT username from admin WHERE username='"+a+"'");
  //5,执行
  if(rs.next()){
     //说明用户名存在
     if(rs.getString(1).equals(b)){
     //一定合法
      response.sendRedirect("guanliyuan.jsp");
     }else{
     //密码错误
     response.sendRedirect("guanliyuandenglu.jsp");
     }
  }else{
     //用户名不存在
     response.sendRedirect("guanliyuandenglu.jsp");
  }
    // 依次关闭
    rs.close() ;
    stmt.close() ;
    conn.close() ;
  %>
  </body>
  
</html>
可是明明数据库里面建好表，也有一个名字和密码在里面，可是执行时却出现以下错误org.apache.jasper.JasperException: An exception occurred processing JSP page /guanliyuanjiance.jsp at line 3229:     %>
30:     <%
31:     //1,加载驱动 
32:     Class.forName("com.microsoft.jdbc.sqlserver.SqlServerDriver");
33:     //2，得到连接 
34:     Connection conn=DriverManager.getConnection("jdbc:microsoft:sqlserver://localhost;DatabaseName=userdb","jie","123");
35:     //3，创建Statement
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:519)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:410)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause javax.servlet.ServletException: java.lang.ClassNotFoundException: com.microsoft.jdbc.sqlserver.SqlServerDriver
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:865)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:794)
org.apache.jsp.guanliyuanjiance_jsp._jspService(guanliyuanjiance_jsp.java:128)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:386)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause java.lang.ClassNotFoundException: com.microsoft.jdbc.sqlserver.SqlServerDriver
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1647)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1493)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:128)
org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:66)
java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
java.lang.Class.forName0(Native Method)
java.lang.Class.forName(Class.java:169)
org.apache.jsp.guanliyuanjiance_jsp._jspService(guanliyuanjiance_jsp.java:93)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:386)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)求高手指点啊