Solr 1.3 was released on September 16, 2008.
If you found a link to this page in some documentation it was there to alert you to the fact that it described a feature that was first introduced in the Solr 1.3 release. Older releases did not have this feature.
Notes About The Release
In Solr 1.3, many classes were moved around. Although classes compiled against 1.2 will run in 1.3, updating class references is recommended.
many classes from org.apache.util moved to org.apache.common.util
many classes from org.apache.solr.request moved to org.apache.solr.common.params