ImageButton显示不出来

这个登陆页面的两个按钮ImageButton，在有的计算机上显示不出来，都是ie6+sp1,很奇怪，有的计算机可以显示出来，有的就显示不出来。那里还需要特殊设置吗？？
<%@ Page language="c#" Codebehind="login.aspx.cs" AutoEventWireup="false" Inherits="Com.Hynet.Ceim.CountyRegion.login" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>系统登录</title>
<meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
<style type="text/css">BODY { BACKGROUND-IMAGE: url(images/FirstBg.gif) }
</style>
<LINK href="css/news.css" rel="stylesheet">
</HEAD>
<body MS_POSITIONING="GridLayout">
<FONT face="宋体"></FONT><FONT face="宋体"></FONT><FONT style="BACKGROUND-COLOR: #ffffff" face="宋体">
</FONT><FONT style="BACKGROUND-COLOR: #ffffff" face="宋体"></FONT><FONT face="宋体"></FONT>
<FONT face="宋体"></FONT><FONT face="宋体"></FONT><FONT face="宋体"></FONT>
<br>
<br>
<br>
<form id="Form1" method="post" runat="server">
<div align="center">
<table width="754" border="0" cellspacing="0" cellpadding="0">
<tr>
<td height="356" background="images/firstlogin.gif" style="WIDTH: 743px">
<table width="98%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td height="60" style="WIDTH: 579px">&nbsp;</td>
<td height="60" style="WIDTH: 136px">&nbsp;</td>
<td height="60">&nbsp;</td>
</tr>
<tr>
<td height="60" style="WIDTH: 579px">&nbsp;</td>
<td height="60" style="WIDTH: 136px">&nbsp;</td>
<td height="60">&nbsp;</td>
</tr>
<tr>
<td height="30" style="WIDTH: 579px">&nbsp;</td>
<td height="30" style="WIDTH: 136px" vAlign="top"><INPUT class="input3" id="txtUserName" style="BORDER-TOP-STYLE: groove; BORDER-RIGHT-STYLE: groove; BORDER-LEFT-STYLE: groove; BORDER-BOTTOM-STYLE: groove"
size="15" runat="server" NAME="txtUserName" maxLength="10"></td>
<td height="30">&nbsp;</td>
</tr>
<tr>
<td height="30" style="WIDTH: 579px">&nbsp;</td>
<td height="30" style="WIDTH: 136px" vAlign="top"><INPUT class="input3" id="txtPassWord" style="BORDER-TOP-STYLE: groove; BORDER-RIGHT-STYLE: groove; BORDER-LEFT-STYLE: groove; BORDER-BOTTOM-STYLE: groove"
size="15" runat="server" NAME="txtPassWord" maxLength="10" type="password"><ASP:CheckBox id="chkPersistCookie" runat="server" autopostback="false" Checked="True" Visible="False" /></td>
<td height="30">&nbsp;</td>
</tr>
<tr>
<td height="50" style="WIDTH: 579px">&nbsp;</td>
<td height="50" style="WIDTH: 136px">
<asp:ImageButton id="ImageButton1" runat="server" ImageUrl="images/Login_Qd.gif"></asp:ImageButton>&nbsp;&nbsp;
<asp:ImageButton id="ImageButton2" runat="server" ImageUrl="images/login_Cx.gif"></asp:ImageButton></td>
<td height="50">&nbsp;</td>
</tr>
</table>
</td>
</tr>
</table>
</div>
</form>
</body>
</HTML>