看到园子里一位同行写的 http://www.cnblogs.com/xiaopeng84/archive/2007/04/10/707093.html
但是没有贴出效果图，自己练了一下，贴出代码和效果：
1 <html xmlns="http://www.w3.org/1999/xhtml"> 2 <head runat="server"> 3 <title></title> 4 <style type="text/css"> 5 .myline{ 6 border-left: #000000 0px solid; 7 border-top: #000000 0px solid; 8 border-right: #000000 0px solid; 9 border-bottom: #000000 1px solid; 10 11 } 12 13 </style> 14 </head> 15 <body> 16 <form id="form1" runat="server"> 17 <div> 18 <asp:TextBox runat="server" ID="txt1" CssClass="myline" Width="80px"></asp:TextBox> 19 </div> 20 </form> 21 </body> 22 </html>