When we develop application, we frequently need to configure it through the configuration file, but I lose the msdn link to the schema explanation most of the time.
for various version of .net framework the link is different, but if you can find one, you can easily choose the other versions as all versions are link in msdn.
here is the link for 3.5 : http://msdn.microsoft.com/en-us/library/1fk1t1t0.aspx
an easily alternative is to look at the framework classes and to figure out the schema, but as i got the link at hand, i want to post it in my blog so that next time i don’t have to look for it.