Banner Tracking HTML Code

I have banners that I want to track. What I want to know is which banner was used to get to site. I want to pass some parameter that gets me that information. I already can get what URL the vistor came from. I dont' need that. I want to know which banners are effective and which are not. I tried passing a parameter like ?source=123. That does not seem to work. What I want is two files. One that that has a banner, gif, whatever. The other is the target file. I need the target to be able to tell me the name of the banner file. I hope I have described it clearly enough. Otherwise send me a comment. Any non - HTML code (whatever you use to read the parameter) has to be ASP. ## Deliverables Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. ## Deadline information Before Nov 1