When passing parameters through query strings you must reset the parameters after each search, otherwise the browser remembers the previous parameters as they are cached and therefore search results may be unpredictable.

To reset parameters append &cbResetParam=1 to your URL.

For example your URL will look like the following:

http://www.yourdomain.com/index?Keyword=Blue&State=CA&Country=USA&cbResetParam=1

As a result with each search the previous values are reset and the new ones are applied. Use the parameter cbResetParam only when required.