I put adsense ads into my site recently and discovered that when I open my site in firefox, and click refresh, sometimes all of the images scatter across the screen and then come back together. When I remove the ads, I don’t have this problem…
It happens more frequently and more severely with pages that have the ad link unit in it (like the home, products, contact page). It happens just for less than a sec. when you refresh the page. i don’t see any problem. It’s basically the way Firefox renders the page, it displays stuff even if it’s not completely ready to be displayed (for faster loading times and such), the adsense is loading a bit slower than your other content. I wouldn’t actually worry about it too much if it were me it’s not really an issue…there is an option in PS to render your code with CSS (although i won’t reccomend because it’s crappy code); try this.