If you want to change multiple webpage inside a iframe which changes in random time gap , Use this code to generate random time spent on website

<iframe src="URL-HERE" id="myFrame" width="1px" marginwidth="0" height="1px" marginheight="0" align="middle" scrolling="no" frameBorder="0"></iframe>

<script>

function getRandomInt(min, max) {

 min = Math.ceil(min);

 max = Math.floor(max);

 return Math.floor(Math.random() * (max - min)) + min;

}

function start()

{

var i = 0;

var url = ["FIRST-URL-HERE","SECOND-URL-HERE","THIRD-URL-HERE"];



var loadpage =  setInterval(function(){

if(i<3) //elements in array must be equal to the given number

{

var loc = url[i];

document.getElementById('myFrame').setAttribute('src', loc);

}

else

{

clearInterval(loadpage);

}

i++;

}, getRandomInt(10000,20000));

}

setTimeout(start,5000);

</script>