Javascript or PHP for swapping HTML Code

Have a look into localStorage. It lets you store stuff (up to 5MB) in the browser. It is persistent and update-able.
You could easily store the number of times the page has been loaded, before then going on to calculate the first element to display.

Perhaps something like this small snippet:
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window.addEventListener('load', onDocLoaded, false);

function onDocLoaded()
{
// page never loaded before - have to add 'timesLoaded' to the localStorage database
if (localStorage.timesLoaded == undefined)
localStorage.timesLoaded = 1;

// page has been loaded previously, 'timesLoaded' already exists, just increment it.
else
{
var numTimes = localStorage.timesLoaded;
numTimes++;
localStorage.timesLoaded = numTimes;
}
var txt = document.createTextNode("Page has been loaded " + localStorage.timesLoaded + " times.");
document.body.appendChild(txt);
}
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Note: There are different methods by which you can access localStorage. Have a read up on it to ensure you use the best one - i.e the one that is supported by all/most browsers. I've simply used one which works in Chrome - no idea which, if any, browsers will fail with my code.