Javascipt Timer

This javascript is for creating a timer on a page using setTimeout method.
you can modify the end condition by removing _PostBack("A", "B") part incase you dont want postback at the end of the time.
var milisec=0
var seconds = 20
var flag = 1


function display(){
if (milisec<=0){
milisec=9
seconds-=1
}
if (seconds<=-1){
milisec=0
seconds+=1
}
else
milisec-=1
document.getElementById("lblTimer").innerHTML=seconds

if (seconds <= 0 && flag == 1) {
flag = 0;
__doPostBack("A", "B");
}
setTimeout("display()",100)
}