This domain points to the OSGeo.nl GitHub repo osgeonl.github.io. 

These are GH pages with custom content like hand-written HTML for the  osgeo.nl website.

Examples:
http://io.osgeo.nl/sitecontent/osgeonl_dag/osgeonl_dag_2012.html
http://io.osgeo.nl/sitecontent/osgeonl_dag/osgeonl_dag_2013.html
http://io.osgeo.nl/sitecontent/osgeonl_dag/osgeonl_dag_2014.html