Strange Code Appears After my URL in Yahoo Results

[Storyman]

It's a small site with just a dozen-and-a-half pages. In the search results the URL for the pages appear normal, but there is a strange code after the main page's URL.

The URL appears as:
http://www.example.com/?q=Affiliate+Program

What the heck is '?q=Affiliate+Program'? I haven't joined any affiliate programs and have no idea what this could mean.

Any ideas?

[edited by: martinibuster at 12:04 am (utc) on Jan. 17, 2006]
[edit reason] examplified URL. [/edit]