防止SQL注入的登录页面

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>防止SQL注入的登录页面</title>
<script type="text/javascript">
    function Mycheck(str){
      var mess="不允许输入的字符：\r\n";
      var mark="yes";
      if(str.indexOf(";")>=0){
          mark="no";
          mess+=" ; ";
      }
      if(str.indexOf("&")>=0){
          mark="no";
          mess+=" & ";
      }
      if(str.indexOf("<")>=0){
          mark="no";
          mess+=" < ";
      }
      if(str.indexOf(">")>=0){
          mark="no";
          mess+=" > ";
      }
      if(str.indexOf("--")>=0){
          mark="no";
          mess+=" -- ";
      }
      if(str.indexOf("/")>=0){
          mark="no";
          mess+=" / ";
      }
      if(str.indexOf("%")>=0){
          mark="no";
          mess+=" % ";
      }
      if(str.indexOf("'")>=0){
          mark="no";
          mess+=" ' ";
      }
      if(mark=="no"){
          alert(mess);
          return false;
      }
      else return 
          return true;      
    }
</script>
</head>
<body style="font-size:12px">
<table width="382" border="0" align="center" cellpadding="0" cellspacing="0">
  <tr>
    <td height="99" background="images/login_01.jpg">&nbsp;</td>
  </tr>
  <tr>
    <td height="160" bgcolor="#FEF7C3"><table width="300" border="0" align="center" cellpadding="3" cellspacing="0">
        <form name="form1" onSubmit="Mycheck(form1.txt_name.value)">
          <tr>
            <td height="22" colspan="2" align="center">&nbsp;</td>
          </tr>
          <tr>
            <td height="22" align="right">管理员:</td>
            <td height="22"><input name="txt_name" type="text" class="textbox" id="txt_name" size="18" maxlength="50"></td>
          </tr>
          <tr>
            <td height="22" align="right">密
              码:</td>
            <td height="22"><input name="txt_passwd" type="password" class="textbox" id="txt_passwd" size="19" maxlength="50"></td>
          </tr>
          <tr>
            <td height="22" colspan="2" align="center"><input name="login" type="submit" id="login" value="登 录" class="button">
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
              <input type="reset" name="Submit2" value="重 置" class="button"></td>
          </tr>
        </form>
    </table></td>
  </tr>
</table>
</body>
</html>