We need the ability to make specific jpg and/or gif images appear on our pages based on the keywords a user typed in google/yah/msn to find us. If we have not spefified a match or if they didn't use a search, it should show a standard image. For example, if someone types in "computer monitor" in google and clicks to our site, the ad might be "monitorsale.jpg", but if they searched "computer disk" the ad might show a computer disc. This has to work for both organic and CPC ads on the 3 SEs mentioned above. This is NOT a graphic design posting. We need a simple code.