SonLight, I'm afraid Blue is right. If you run a business, then having advertising displayed on your web site is not a very serious decision. Not only it will affect those who visit - it will confuse your current clients as well.

If you still want to serve advertising on your site and control what gets to be displayed, there is no better way than to just quit AdSense program and simply sell space yourself to those clients you want. That way you don't have to worry about hosting competitors being advertised on top of your site at your marketing expense when you spend money to attract customers to your web site.

Best,