I'm editing a code.. I'm wondering why's the username and password are autofillup.. I mean there's a default Username and Password.. How can I remove that?

Look for the file containing the default values, change them to something nobody else knows.

... and add into form tag <form ..... autocomplete="off">

I think this code will help you to resolve your problem. I am using Jquery so I have solution regarding that.

$('#<your input id>').autocompleter = null;

that very very easy .. add into form tag <form ..... autocomplete="off">......and that username and password don't appear again.

Into HTML5:
In some browsers you may need to activate the autocomplete function for this to work.

Browsers who support attribute "autocomplete": IE 8, FF 3.5, Opera 9.5, Chrome 3.0, Safari 4.0

@everyone
thanks for the reply