It's possible to open a specific infowindow of a location/placemark in a kml file. You have to use the geoxml kml renderer to make it work.
To the url of the article you have to add url parameters. Not to the url of the kml!

You can use two different parameters:

• openbyname - Open an infowindow of a placemark based on the ID of the placemark
• openbyid - Open an infowindow of a placemark based on the name of the pacemark (first name that is found will be opened)

For example: http://tech.reumer.net/Google-Maps/Demo-Google-Maps-v3/kml-sidebar.html?openbyname=Doubletree Grand Key Resort

The syntax for the placemark in KML is:

<Placemark id="ID">
  <name>...</name>