hi all,

i have to try to check whether my login information is correct or not, it's just contain username and password only. here is my config.txt content :

user1, user2, user3
and here is my html index file :

and here is my code to check login info.

everything is correct to check if the username was exists in text file but when I type wrong username (another user beside in notepad) it's just show me blank page cause I didn't know what code should i type in there

what should i do ?