已在页面完全加载前强制排版。若样式表尚未加载，则可能会导致无样式内容闪烁。怎么解决啊？求大神告知。

这是代码部分....

<?php 
//注册处理界面 regcheck.php
 if(isset($_POST["Submit"]) && $_POST["Submit"] == "注册") 
 { 
 $user = $_POST["username"]; 
 $psw = $_POST["userpwd"]; 
 $psw_confirm = $_POST["confirm"]; 
 if($user == "" || $psw == "" || $psw_confirm == "") 
 { 
 echo "<script>alert('请确认信息完整性！'); history.go(-1);</script>"; 
 } 
 else 
 { 
 if($psw == $psw_confirm) 
 { 
 $conn = pg_connect ("host=localhost port=5432 dbname=tangtang user=postgres password=200018"); //连接数据库,帐号密码为自己数据库的帐号密码 
 if(pg_last_error($conn)){
 echo pg_last_error($conn);
 exit;
 }
 $rec = pg_select($conn,'userdb',$_POST);
 $sql = "select username from user where username = '$user'"; //SQL语句
 $result = pg_query($conn,$sql); //执行SQL语句 
 $num = pg_num_rows($result); //统计执行结果影响的行数 
 
 if($num) //如果已经存在该用户 
 { 
 echo "<script>alert('用户名已存在'); history.go(-1);</script>"; 
 } 
 else //不存在当前注册用户名称 
 { 
 $sql_insert = "insert into `user` (`username`,`userpwd`) values('" . $user . "','" . $psw ."')"; 
 $res_insert = pg_query($conn,$sql_insert); 

 if($res_insert) 
 { 
 echo "<script>alert('注册成功！'); history.go(-1);</script>"; 
 } 
 else 
 { 
 echo "<script>alert('系统繁忙，请稍候！'); history.go(-1);</script>"; 
 } 
 } 
 } 
 else 
 { 
 echo "<script>alert('密码不一致！'); history.go(-1);</script>"; 
 } 
 } 
 } 
 else 
 { 
 echo "<script>alert('提交未成功！');</script>"; 
 } 
?>