各位帮忙看下为何总是提示验证码不正确呢，请问如何

//form表单部分
<form action="Check_Login.jsp" method="post" name="check_login_info" onSubmit="return check(this)">
                      <table width="100%" border="0" class="bodystyle">
                        <tr> 
                          <td colspan="3">&nbsp;</td>
                        </tr>
                        <tr> 
                          <td class="wahfengmid"><div align="right"></div></td>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td class="wahfengmid"><div align="right"></div></td>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td class="wahfengmid"><div align="right"></div></td>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr>
                          <td class="wahfengmid"><div align="right"></div></td>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td width="35%" class="wahfengmid"><div align="right"></div></td>
                          <td width="58%">&nbsp;</td>
                          <td width="7%">&nbsp;</td>
                        </tr>
                        <tr> 
                          <td class="wahfengmid"><div align="right" class="wahfengmid">管理帐号：</div></td>
                          <td>
<input name="usr_id" type="text" id="usr_id"  style="background-image: url('images/pwd_bg.jpg'); color: #FF0000" size="24"></td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td><div align="right"></div></td>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td><div align="right" class="wahfengmid">管理密码：</div></td>
                          <td>
<input name="usr_pwd" type="password" id="usr_pwd" style="background-image: url('images/pwd_bg.jpg'); color: #FF0000" size="24"></td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td><div align="right"><span class="wahfengmid">验 证 码：</span></div></td>
                          <td>
                            <div align="left"> 
                              <input name="my_check_t" type="text" id="my_check_t"  style="background-image: url('images/pwd_bg.jpg'); color: #FF0000" size="10" maxlength="8">
                              <span class="unnamed1">
                             <%
int number=(int)(Math.random()*1000000)+1;
out.print(number);%>
 
                              <input name="my_check_h" type="hidden" id="my_check_h" value="<%=number%>">
                              </span>                            </div></td>
                          <td>&nbsp;</td>
                        </tr>
                        <tr> 
                          <td colspan="3">&nbsp;</td>
                        </tr>
                        <tr> 
                          <td colspan="3"><div align="center" class="wahfengmid"> 
                              <p> 
                                <input type="submit" name="Submit" value="点击进入管理系统" style="background-image: url('images/Button_bg.jpg'); font-weight: bold">
                              </p>
                            </div></td>
                        </tr>
                      </table>
                    </form><///判断页面
<%
String checkt,checkh;
checkt=request.getParameter("my_check_t");
checkh=request.getParameter("my_check_h");
if(checkt!=checkh);
{
    out.print("<script>window.alert('验证码不正确');window.location.href='index.jsp'</script>");
}
%>