Today when i logged into my account to create a new Adcode, I could see that the entire structure of the google adsense code has changed. No prizes for guessing what happend? It’s a new feature from adsense which lets you easily manage your ad units from within your AdSense account.
“This new ad management feature means that your ad unit settings (such as colors and channels) for new AdSense for content ad units will be saved in your AdSense account every time you generate ad code. Then, if you’d like to change any of these settings in the future, all you do is make the update within your account — you’ll no longer need to manually replace the ad code on all of your pages. For instance, you can quickly change the borders of all your 300×250 medium rectangles from red to blue with just a few mouse clicks. ”
You make a 250 x 250 Add in adsense now it gets saved and later you can change the color of the add from within the adsense account. So you dont have to copy and edit your webpage again when your site has a color change or you decide to change your adsense color.
Earlier add codes also works fine if you havent updated to new code, But it’s always suggested that you keep up with the tide and make changes to your code now and forget about editing your adsense code in website again. Cool feature!
Screenshots : Credits Adsense Blog