The “simplest” thing is probably to create a user input that listens for keys and stores the actual key values with a simple • or * display in the field.
* , , .
, , , , . backspace .., .
: http://jsfiddle.net/d94P5/
<input type="text" id="password">
<input type="text" id="hiddenValue">
Javascript
var field = document.getElementById("password")
var realValue = "";
field.onkeydown = function(evt){
realValue += String.fromCharCode(evt.keyCode)
this.value = realValue.replace(/./g,"*");
document.getElementById("hiddenValue").value = realValue
return false;
}