Countdown timer

Hello everyone, I have this script and i don't know why doesn't work. I want to display a timer on page a index.html, after 15 sec, the page is reloaded and appears other content...how can I do that?
<script type="text/javascript">
var cnt = 15;
function countdown() {
if (cnt == -1) {
window.location.href = "index.html";
} else {
/*
min = Math.floor(cnt / 60);
sec = cnt - (min * 60);
if (sec < 10) { sec = "0" + sec; }
if (min < 10) { min = "0" + min; }
document.getElementById('timercountdown').innerHTML = min + ":" + sec;
*/
if (cnt <= 1) {
measurement = "second";
} else {
measurement = "seconds";
}

document.getElementById('timercountdown').innerHTML = cnt + " " + measurement;
cnt--;
_timer = setTimeout("countdown()", 1000);
}
}
var _timer = setTimeout("countdown()", 1000); // start ticking process
</script>
Please wait for another <span id="timercountdown"></span> while the page is loading...
Click "here" if you want to start immediately.

 

<script type="text/javascript">
var cnt = 14;
function countdown() {
 
    if (cnt <= 1) {
      measurement = "second";
    } else {
      measurement = "seconds";
    }
    if(cnt==-1){
      window.location.href='http://google.com';
      
      //document.getElementById('hidden').style.display="block";
      //document.getElementById('timer').style.display="none";
      
    }else{
      document.getElementById('timercountdown').innerHTML = cnt + " " + measurement;
      cnt--;
      _timer = setTimeout("countdown()", 1000);
    }
}

var _timer = setTimeout("countdown()", 1000); // start ticking process
</script>
Please wait for another <span id="timercountdown">15 seconds</span> while the page is loading...
Click "here" if you want to start immediately.

Code (markup):

 

how does it not work? you do need to define 'measurement', under var cnt, have var measurement;

 

You do not understand me, I want to appear this countdown timer on a page "index.html" and after the counter reaches 0,the page is reloaded ,the counter disappears and other content appears on the same page (index.html)...


The script that I posted above, it's something like when the counter reaches 0, the page is reloaded but it appears again, and I want to appears something else.

 

Do redirect to another page instead of reload the same page.

Or pass a parameter in JS to URL and read it (best on server side) and return the same page without counter functionality.

 

I do not know javascript very well, can you give me a concrete example?

 

index.html:

<script type="text/javascript">
var cnt = 15;
function countdown() {
if (cnt == -1) {
window.location.href = "index2.html";
} else {
/*
min = Math.floor(cnt / 60);
sec = cnt - (min * 60);
if (sec < 10) { sec = "0" + sec; }
if (min < 10) { min = "0" + min; }
document.getElementById('timercountdown').innerHTML = min + ":" + sec;
*/
if (cnt <= 1) {
measurement = "second";
} else {
measurement = "seconds";
}

document.getElementById('timercountdown').innerHTML = cnt + " " + measurement;
cnt--;
_timer = setTimeout("countdown()", 1000);
}
}
var _timer = setTimeout("countdown()", 1000); // start ticking process
</script>

Code (markup):

index2.html

Your page here

Code (markup):