Go to your Google AdSense Account. Use these settings. You can choose other colors but the border and the background must be the same.
Open Photoshop. And make the new file 30 pixels bigger than the Adsense ad.
Make something like this with the lasso tool.
Use these setting. Fill the background with the background color of your website where you put your Google Adsense ad.
Open Dreamweaver. Insert a table. Use the picture you just made for the table background. Paste the Google Adsense code.
Use Center and Middle for the alignment of the table.