Weird happenings on transfer of Wordpress site

I recently sold a WP site, and having transferred it over to the buyer we’re both stumped as to what’s happened. He’s made a few design changes, deleting some widgets and adding his own ads. But the changes only appear when using www in front of the domain. Without, it still appears the same as when I had the site. It was always set without the www in the general setting, and still is now.

url is below in my sig.

Any ideas would be appreciated. Thanks.

One word: WP-Super-Cache.

Look at the end of the HTML for the two versions of the page.

Thank you very much Dan, I knew it had to be something simple. Much appreciated!