js控制层居中显示

Question

javascript 如何控制一个层 在屏幕中间显示？不管浏览器怎麽调大小都居中显示,该怎么写

Answer 1

<div   style="width:400px;height:300px;margin-top:-150px;margin-left:-300px;left:50%;top:50%;position:absolute"> 
     <table id="__01" width="590" height="340" border="0" cellpadding="0" cellspacing="0" align="center">
      
<tr>
<td colspan="3">
            <img src="images/dl_01.jpg" /></td>
</tr>
<tr>
<td>
            <img src="images/dl_02.jpg" /></td>
<td bgcolor="#C6DFEF">
<table height="89" border="0" cellpadding="0" cellspacing="0" style="width: 244px">
              <tr>
                <td align="right" style="width: 112px"><img src="images/ren.gif"></td>
                <td style="width: 150px">用户名：</td>
                <td align=left style="width: 180px">
                    <table cellpadding="0" cellspacing="0" border="0">
                        <tr>
                            <td>
                    <asp:TextBox ID="LogonIDTB" runat="server"></asp:TextBox></td>
                        </tr>
                    </table>
                </td>
              </tr>
              <tr>
                <td align="right"><img src="images/pass.gif" width="21" height="28"></td>
                <td>密&nbsp;&nbsp; 码：</td>
                <td align=left>
                    <table cellpadding="0" cellspacing="0" border="0"><TBODY><TR><TD><asp:TextBox id="PWDTB" runat="server" TextMode="Password"></asp:TextBox></TD></TR></TBODY></table></td>
              </tr>
              <tr>
                  <td align="right">
                      <img height="28" src="images/yanzheng.gif" width="21" /></td>
                  <td>
                      验证码：</td>
                  <td align="left">
                      <table border="0" cellpadding="0" cellspacing="0">
                          <tbody>
                              <tr>
                                  <td>
                                      <asp:TextBox ID="txtCheckCode" runat="server" Width="65px"></asp:TextBox></td>
                                  <td>
                                      <img src="ValidateCode.aspx" id="IMG1"/></td>
                              </tr>
                          </tbody>
                      </table>
                  </td>
              </tr>
   <tr>
<td>
  </td>
<td border="0" cellpadding="0" cellspacing="0"></td>
  <td style="text-align: left; width: 180px;" align="right">
      &nbsp; &nbsp;
          <asp:Button ID="Button1" OnClick="Button1_Click" runat="server" Text="登　陆">
          </asp:Button></td></tr>
            </table>
</td>
<td style="width: 57px">
            <img src="images/dl_04.jpg" /></td>
</tr>
<tr>
<td colspan="3">
            <img src="images/dl_05.jpg" /></td>
</tr>
</table>
</div> 

Answer 2

.div 
   { 
  position:absolute; 
  top:50%; 
  left:50%; 
  margin:-100px   0   0   -100px; 
 width:209px; 
 height:106px; 
 Z-INDEX:9999999;
 CURSOR:hand;
 background-image:url('../images/login_loader_01.gif');   
} 
设层的class为div