Wednesday, October 13, 2010

Speed up page load times when running Google ads

Google ads are an easy way to monetize your site, but their implementation leaves a lot to be desired. To insert a Google ad block on a page one has to insert two script blocks: one to set the adverts parameters, and one to load the external Google script.
The problem is that the scripts have to be inserted in the body at the place where the advert is desired. This is because Google uses JavaScript's document.write to generate an iframe, which then loads the ad. If Google's servers are being a bit laggy then your visitor has to wait for the Google script to finish loading before the rest of the page is rendered. The closer your ad is to the top of the page, the worse the resulting problem is.
A number of solutions have been proposed, including overwriting the document.write method, and inserting the Google script through DOM manipulation. Unfortunately this breaks in Safari 2.0, and breaks any other instances of document.write you may be using.
So here is the solution we've come up with:

Normal set-up


<html>
...
<body>
Content above advert
<script type="text/javascript"><!--
Google ad params
//--></script>
<script type="text/javascript" src="...show_ads.js"></script>
Content below advert
</body>
</html>

Optimised set-up


<html>
...
<body>
Content above advert
<div id="ad1_inline"></div>
Content below advert
<div id="ad1_footer" style="display: none;">
<script type="text/javascript"><!--
<em>Google ad params</em>
//--></script>
<script type="text/javascript" src="...show_ads.js"></script>
</div>
<script type="text/javascript">
window.onload = function() {
document.getElementById('ad1_inline').appendChild(document.getElementById('ad1_footer'));
document.getElementById('ad1_footer').style.display = '';
}
</script>
</body>
</html>

What it does

  1. Creates a place-holder div for the where the ad will end up
  2. Places all the ad code in an "footer div" at the bottom of the page - this prevents your page from "locking" while the Google scripts load
  3. Hides the footer "footer div" with css so the ads don't ever show below your page, causing the page height to "jump"
  4. Waits for the whole page to load before moving the ads (the window.onload bit) thus preventing Internet Explorer from getting really upset.
  5. Moves the ad to it's placeholder, and un-hides it
Of course you may not want to use window.onload. If you attach the function to an event you can modularise the whole ad insertion in your code. Using a JavaScript library (Prototype in this case, but others will look similar) results in the following change to the last script:

...
<script type="text/javascript">
Event.observe(window, 'load', function() {
$('ad1_inline').appendChild($('ad1_footer'));
$('ad1_footer').show();
}
</script>
...
All scripts are Public Domain.


source: http://semplicewebsites.com/google-ads

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